Light ranging device with mems scanned emitter array and synchronized electronically scanned sensor array

ABSTRACT

Embodiments describe a solid state electronic scanning LIDAR system that includes a scanning focal plane transmitting element and a scanning focal plane receiving element whose operations are synchronized so that the firing sequence of an emitter array in the transmitting element corresponds to a capturing sequence of a photosensor array in the receiving element. During operation, the emitter array can sequentially fire one or more light emitters into a scene and the reflected light can be received by a corresponding set of one or more photosensors through an aperture layer positioned in front of the photosensors. Each light emitter can correspond with an aperture in the aperture layer, and each aperture can correspond to a photosensor in the receiving element such that each light emitter corresponds with a specific photosensor in the receiving element.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/528,879, filed on Jul. 5, 2017, the disclosure of which isincorporated herein by reference in its entirety and for all purposes.

BACKGROUND

Light imaging, detection and ranging (LIDAR) systems measure distance toa target by illuminating the target with a pulsed laser light andmeasuring the reflected pulses with a sensor. Time-of-flightmeasurements can then be used to make a digital 3D-representation of thetarget. LIDAR systems can be used for a variety of applications where 3Ddepth images are useful including archaeology, geography, geology,forestry, mapping, construction, medical imaging and militaryapplications, among others. Autonomous vehicles can also use LIDAR forobstacle detection and avoidance as well as vehicle navigation.

Some LIDAR systems include a mechanical, moving component thatphysically scans a transmitting and receiving element around arotational angle of less than or equal to 360° to capture an image of ascene in a field. One example of such a system that can be used forobstacle detection and avoidance in vehicles is often referred to as arotating or spinning LIDAR system. In a rotating LIDAR system, a LIDARsensor is mounted, typically within a housing, to a column that rotatesor spins a full 360 degrees. The LIDAR sensor includes coherent lightemitters (e.g., pulsed lasers in the infrared or near-infraredspectrums) to illuminate a scene around the vehicle as the LIDAR sensoris continuously rotated through the scene. As the coherent lightemitters spin around, they send pulses of radiation away from the LIDARsystem in different directions in the scene. Part of the radiation,incident on surrounding objects in the scene, is reflected from theseobjects around the vehicle, and then these reflections are detected bythe imaging system portion of the LIDAR sensor at different timeintervals. The imaging system turns the detected light into electricsignal.

In this way, information about objects surrounding the LIDAR systemincluding their distances and shapes is gathered and processed. Adigital signal processing unit of the LIDAR system can process theelectric signals and reproduce information about objects in a depthimage or a 3D point cloud that can be used as an aid in obstacledetection and avoidance as well as for vehicle navigation and otherpurposes. Additionally, image processing and image stitching modules cantake the information and assemble a display of the objects around thevehicle.

Another type of mechanical LIDAR system scans a laser beam along apredetermined scan pattern using, for example, a mirror galvanometer.Some such systems can include a two-dimensional array of photosensorsthat are electronically scanned to coincide with the scan pattern of thelaser beam. It can be challenging, however, to calibrate and synchronizethe sensor array with laser beam when a mechanical system is employedfor steering the beam.

Solid-state LIDAR systems also exist that do not include any movingmechanical parts. Instead of rotating through a scene, some solid stateLIDAR systems flash an entire portion of a scene they intend to capturewith light and sense the reflected light. In such systems, thetransmitter includes an array of emitters that all emit light at once toilluminate the scene, and are thus sometimes referred to as “flash”LIDAR systems. Flash LIDAR systems are less complicated to make becauseof the lack of moving parts; however, they can require a large amount ofpower to operate since all of the emitters are activated at once andthey can require a large amount of processing power to process signalsfrom all the pixel detectors at once. Decreasing the number of lightemitters can save power at the sacrifice of quality and resolution ofthe resulting image. The large amount of light emitted can also inducean undesirable amount of stray light that can generate noise at thereceiving end, thereby decreasing the signal-to-noise ratio of thesensed signals and resulting in blurred images.

SUMMARY

Some embodiments of the disclosure pertain to stationary, solid-stateLIDAR systems in which there is no spinning column or mirrorgalvanometers. Embodiments can capture the image of a scene at a highresolution and low power consumption and with improved accuracy,reliability, size, integration and appearance as compared to currentlyavailable spinning LIDAR systems.

According to some embodiments, a solid state electronic scanning LIDARsystem can include a scanning focal plane transmitting element and ascanning focal plane receiving element whose operations are synchronizedso that the firing sequence of an emitter array in the transmittingelement corresponds to a capturing sequence of a photosensor array inthe receiving element. The transmitting element and receiving elementcan each be coupled with image space telecentric bulk optics thatcollimate the transmitter and receiver fields of view, respectively, inobject space.

During operation, the emitter array can sequentially fire one or morelight emitters into a scene and the reflected light can be received by acorresponding set of one or more photosensors through an aperture layerpositioned in front of the photosensors. Each light emitter cancorrespond with an aperture in the aperture layer, and each aperture cancorrespond to a photosensor in the receiving element such that eachlight emitter corresponds with a specific photosensor in the receivingelement. The aperture can mitigate the exposure of stray light onneighboring photosensors as well as narrow the field of view for aphotosensor to a single point in the field. By synchronizing the firingand capturing sequences, the solid-state scanning LIDAR system canefficiently capture images by only illuminating, at a given point intime, a certain amount of light from a set of emitters that can beefficiently detected by a corresponding set of photosensors, therebyminimizing excessive illumination of a scene and concentrating energy ina manner that makes the best possible use of the available power to thesystem. Furthermore, electronic scanning LIDAR systems in embodimentsherein can also utilize micro-optics to further improve the efficiencyat which images of a scene are captured. The micro-optics can improvethe brightness and intensity of light emitted from a transmittingelement as well as minimize cross-talk between sensor pixels of areceiving element of the electrically scanning LIDAR system.

A solid-state scanning LIDAR system according to some embodiments of thedisclosure can include a scanning focal plane array for the receivingelement and a microelectromechanical system (MEMS) one-dimensionalscanning mirror coupled to a transmitting element. In some embodimentsthe transmitter element can be a one-dimensional array of emittersoriented perpendicular to the scanning axis of the MEMS mirror, and insome other embodiments the transmitter element can be a single emitterwith a diffractive element of another optical element to create a laserline coupled with the MEMS mirror or multiple emitters behind multiplediffractive optical elements to enable electronic scanning.

In some embodiments, a solid state optical system includes a lighttransmission module including a transmitter layer having an array ofindividual light emitters, a light sensing module including a sensorlayer that has an array of photosensors, emitter array firing circuitrycoupled to the array of light emitters and configured to activate only asubset of light emitters at a time, and sensor array readout circuitrycoupled to the array of photosensors and configured to synchronize thereadout of individual photosensors within the array concurrently withthe firing of corresponding light emitters so that each light emitter inthe array of individual light emitters can be activated and eachphotosensor in the array of photosensors can be readout through oneemission cycle. Each light emitter in the array of light emitters can bepaired with a corresponding photosensor in the light sensing module.

In some additional embodiments, a solid state optical system forperforming distance measurements includes a light emission systemincluding a bulk transmitter optic and an illumination source includinga two-dimensional array of light emitters arranged according to anillumination pattern and aligned to project discrete beams of lightthrough the bulk transmitter optic into a field ahead of the opticalsystem. The solid state optical system also includes a light detectionsystem including a bulk receiver optic, an aperture layer including aplurality of apertures, and a photosensor layer including atwo-dimensional array of photosensors configured to detect photonsemitted from the illumination source and reflected from surfaces withinthe field after passing through the bulk receiver optic. The aperturelayer and the photosensor layer can be arranged to form a plurality ofsense channels arranged in a sensing pattern that corresponds to theillumination pattern and where each sense channel in the plurality ofsense channels corresponds to an emitter in the array of emitters andincludes an aperture from the aperture layer and a photosensor from thephotosensor layer. The solid state optical system also includes emitterarray firing circuitry coupled to the two-dimensional array of lightemitters and configured to activate only a subset of light emitters at atime, and sensor array readout circuitry coupled to the two-dimensionalarray of photosensors and configured to synchronize the readout ofindividual photosensors within the array concurrently with the firing ofcorresponding light emitters so that each light emitter in the array ofindividual light emitters can be activated and each photosensor in thearray of photosensors can be readout through one emission cycle.

In certain embodiments, a solid state optical system for performingdistance measurements includes a light emission system including a bulktransmitter optic and an illumination source including a two-dimensionalarray of light emitters aligned to project discrete beams of lightthrough the bulk transmitter optic into a field external to the opticalsystem according to an illumination pattern in which each discrete beamin the illumination pattern represents a non-overlapping field-of-viewwithin the field. The solid state optical system also includes a lightdetection system configured to detect photons emitted from theillumination source and reflected from surfaces within the field, thelight detection system including a bulk receiver optic, an aperturelayer including a plurality of apertures, and a photosensor layerincluding a two-dimensional array of photosensors, where the aperturelayer and the photosensor layer are arranged to form a plurality ofsense channels having a sensing pattern in the field that substantiallymatches, in size and geometry across a range of distances from thesystem, the illumination pattern of the array of light emitters, andwhere each sense channel in the plurality of sense channels correspondsto an emitter in the array of emitters and includes an aperture from theaperture layer and a photosensor from the photosensor layer. The solidstate optical system also includes emitter array firing circuitrycoupled to the array of light emitters and configured to execute aplurality of image capture periods where, for each image capture periodthe emitter array firing circuitry sequentially fires subsets ofemitters within the array of light emitters according to a firingsequence until the illumination pattern is generated, and sensor arrayreadout circuitry coupled to the array of photosensors and configured tosynchronize the readout of individual photosensors within the arrayconcurrently with the firing of corresponding emitters within the arrayof light emitters.

In some embodiments, a solid state optical system for performingdistance measurements includes a first illumination source including afirst two-dimensional array of light emitters aligned to projectdiscrete beams of light into a field external to the optical systemaccording to a first illumination pattern, a second illumination sourceincluding a second two-dimensional array of light emitters aligned toproject discrete beams of light into the field according to a secondillumination pattern having a same size and geometry as the firstillumination pattern, and a light detection module including an array ofphotosensors configured to detect photons emitted from the first andsecond illumination sources and reflected from surfaces within thefield, where each photosensor in the array of photosensors has afield-of-view that overlaps with a field-of-view of one emitter from thefirst array of light emitters and one emitter from the second array oflight emitters. The first and second arrays of light emitters and thearray of photosensors can operate in synchronization such that when oneor more light emitters are activated, a corresponding one or more of thephotosensors are read.

In some additional embodiments, a solid state optical system forperforming distance measurements includes a first light emission moduleincluding a first bulk transmitter optic and a first illumination sourceincluding a first two-dimensional array of light emitters aligned toproject discrete beams of light through the first bulk transmitter opticinto a field external to the optical system according to a firstillumination pattern, a second light emission module including a secondbulk transmitter optic and a second illumination source including asecond two-dimensional array of light emitters aligned to projectdiscrete beams of light through the second bulk transmitter optic intothe field according to a second illumination pattern having a same sizeand geometry as the first illumination pattern, and a light detectionmodule including a bulk receiver optic, an aperture layer including aplurality of apertures, and a photosensor layer including an array ofphotosensors configured to detect photons emitted from the first andsecond illumination sources and reflected from surfaces within the fieldthrough the bulk receiver optic, where the aperture layer and thephotosensor layer are arranged to form a two-dimensional array of sensechannels, each sense channel including an aperture from the aperturelayer and a photosensor from the photosensor layer and having afield-of-view that overlaps with a field-of-view of one emitter from thefirst emitter array and one emitter from the second emitter array. Thefirst and second arrays of light emitters and the array of photosensorscan operate in synchronization such that when one or more light emittersare activated, a corresponding ones of the photosensors are read.

In certain embodiments, a solid state optical system for performingdistance measurements includes a light detection system including a bulkreceiver optic, an aperture layer including a plurality of apertures,and a photosensor layer including a two-dimensional array ofphotosensors, where the aperture layer and the photosensor layer arearranged to form a plurality of sense channels having a sensing patternwith each sense channel in the plurality of sense channels defining adiscrete, non-overlapping field-of-view beyond a threshold distance in afield ahead of the light detection system and including an aperture fromthe aperture layer and a photosensor from the photosensor layer. Thesolid state optical system also includes a light emission systemincluding a first bulk transmitter optic, a first two-dimensional arrayof light emitters aligned to project discrete beams of light through thefirst bulk transmitter optic into the field according to a firstillumination pattern, a second bulk transmitter optic, and a secondtwo-dimensional array of light emitters aligned to project discretebeams of light through the second bulk transmitter optic into the fieldaccording to a second illumination pattern having a same size andgeometry as the first illumination pattern, where the first and secondillumination patterns are aligned such that one discrete beam from thefirst illumination pattern and one discrete beam from the secondillumination pattern falls within the field-of-view of each sensechannel in the plurality of sense channels. The solid state opticalsystem also includes emitter array scanning circuitry coupled to thefirst and second arrays of light emitters and configured to execute aplurality of image capture periods where, for each image capture periodthe emitter array scanning circuitry sequentially fires a subset ofemitters from the first emitter array followed by a subset of emittersfrom the second emitter array until the first and second illuminationpatterns are generated, and sensor array scanning circuitry coupled tothe array of photosensors and configured to synchronize the readout ofindividual photosensors within the array concurrently with the firing ofcorresponding emitters within the first and second arrays of lightemitters.

In some embodiments, an optical system for performing distancemeasurements includes an illumination source having a column of lightemitters aligned to project discrete beams of light into a fieldexternal to the optical system, a MEMS device configured to tilt along ascanning axis oriented perpendicular to the column of light emitters andreflect radiation from the column into the field to produce atwo-dimensional illumination pattern in which the discrete beams fromthe column of light emitters are repeated multiple times formingmultiple non-overlapping columns within the pattern, and a lightdetection system configured to detect photons emitted from theillumination source and reflected from surfaces within the field, thelight detection system including a photosensor layer including atwo-dimensional array of photosensors having a sensing pattern in thefield that substantially matches, in size and geometry across a range ofdistances from the system, the two-dimensional illumination patterncreated by the MEMS device. The optical system also includes circuitrycoupled to the MEMS device and the column of light emitters andconfigured to execute a plurality of image capture periods where, foreach image capture period, the column of light emitters is sequentiallyfired while the MEMS device is tilted along its axis until theillumination pattern is generated, and sensor array scanning circuitrycoupled to the array of photosensors and configured to synchronize thereadout of individual photosensors within the array concurrently withthe firing of corresponding emitters within the column of lightemitters.

In some additional embodiments, an optical system for performingdistance measurements includes a light emission system having a bulktransmitter optic and an illumination source including a column of lightemitters aligned to project discrete beams of light through the bulktransmitter optic into a field external to the optical system, a MEMSdevice disposed between the bulk transmitter optic and the illuminationsource, the MEMS device configured to tilt along a scanning axisoriented perpendicular to the column of light emitters and reflectradiation from the column into a field external to the optical system toproduce a two-dimensional illumination pattern in which the discretebeams from the column of light emitters are repeated multiple timesforming multiple non-overlapping columns within the pattern, and a lightdetection system configured to detect photons emitted from theillumination source and reflected from surfaces within the field, thelight detection system including a bulk receiver optic, an aperturelayer including a plurality of apertures, and a photosensor layerincluding a two-dimensional array of photosensors, where the aperturelayer and the photosensor layers are arranged to form a plurality ofsense channels having a sensing pattern in the field that substantiallymatches, in size and geometry across a range of distances from thesystem, the two-dimensional illumination pattern created by the MEMSdevice, and where each sense channel in the plurality of sense channelscorresponds to an emitter in the array of emitters and includes anaperture from the aperture layer and a photosensor from the photosensorlayer. The optical system also includes circuitry coupled to MEMS deviceand the column of light emitters and configured to execute a pluralityof image capture periods where, for each image capture period the columnof light emitters is sequentially fired while the MEMS device is tiltedalong its axis to until the illumination pattern is generated, andsensor array scanning circuitry coupled to the array of photosensors andconfigured to synchronize the readout of individual photosensors withinthe array concurrently with the firing of corresponding emitters withinthe array of light emitters.

In certain embodiments, an optical system for performing distancemeasurements includes a light emission system having a bulk transmitteroptic and an illumination source including a single light emitteraligned to a project discrete beam of light through the bulk transmitteroptic into a field external to the optical system, an optical elementdisposed between the bulk transmitter optic and the illumination sourceand configured to generate a spot pattern from the single light emitter,a MEMS device disposed between the optical element and the illuminationsource, the MEMS device configured to tilt along a scanning axis andreflect radiation from the single light emitter into a field external tothe optical system to produce a two-dimensional illumination pattern inwhich the spot pattern of light is repeated multiple times formingmultiple non-overlapping columns within the pattern, and a lightdetection system configured to detect photons emitted from theillumination source and reflected from surfaces within the field, thelight detection system including a bulk receiver optic, an aperturelayer including a plurality of apertures, and a photosensor layerincluding a two-dimensional array of photosensors, where the aperturelayer and the photosensor layers are arranged to form a plurality ofsense channels having a sensing pattern in the field that substantiallymatches, in size and geometry across a range of distances from thesystem, the two-dimensional illumination pattern created by the MEMSdevice, and where each sense channel in the plurality of sense channelscorresponds to a spot within the two-dimensional illumination patternand includes an aperture from the aperture layer and a photosensor fromthe photosensor layer. The optical system also includes circuitrycoupled to MEMS device and the single light emitter and configured toexecute a plurality of image capture periods where, for each imagecapture period the single light emitter is sequentially fired while theMEMS device is tilted along its axis until the illumination pattern isgenerated, and sensor array scanning circuitry coupled to the array ofphotosensors and configured to synchronize the readout of individualphotosensors within the array concurrently with the firing of the singlelight emitter.

In some embodiments, an optical system for performing distancemeasurements includes a two-dimensional array of light emitters alignedto project the discrete beams of light into a field external to theoptical system according to an illumination pattern in which eachdiscrete beam in the illumination pattern represents a non-overlappingfield-of-view within the field, and a light detection system including aphotosensor layer formed of a two-dimensional array of photosensors, thetwo-dimensional array of photosensors including a first subset ofphotosensors positioned to correspond with a first light emitter of thearray of light emitters such that a field of view of the first lightemitter overlaps with at least a portion of each field of view of eachphotosensor in the first subset of photosensors, where each photosensorin the first subset of photosensors is configured to receive at least aportion of light emitted from the first light emitter.

In some additional embodiments, an optical system for performingdistance measurements includes a light emission system configured toemit discrete beams of light into a field, the light emission systemincluding a bulk transmitter optic and a two-dimensional array of lightemitters aligned to project the discrete beams of light through the bulktransmitter optic into a field external to the optical system accordingto an illumination pattern in which each discrete beam in theillumination pattern represents a non-overlapping field-of-view withinthe field, and a light detection system configured to detect photonsemitted from the illumination source and reflected from surfaces withinthe field, the light detection system including a bulk receiver opticand a photosensor layer formed of a two-dimensional array ofphotosensors including a first subset of photosensors positioned tocorrespond with a first light emitter of the array of light emitterssuch that a field of view of the first light emitter overlaps with atleast a portion of each field of view of each photosensor in the firstsubset of photosensors, each photosensor in the first subset ofphotosensors is configured to receive at least a portion of lightemitted from the first light emitter. The optical system also includesemitter array firing circuitry coupled to the array of light emittersand configured to execute a plurality of capture periods where, for eachcapture period the emitter array firing circuitry sequentially firessubsets of emitters within the array of light emitters according to afiring sequence until the illumination pattern is generated, and sensorarray readout circuitry coupled to the array of photosensors andconfigured to synchronize the readout of individual photosensors withinthe array concurrently with the firing of corresponding emitters withinthe array of light emitters.

In certain embodiments, an optical system for performing distancemeasurements includes a light emission system configured to emitdiscrete beams of light into a field, the light emission systemincluding a bulk transmitter optic and a two-dimensional array of lightemitters aligned to project the discrete beams of light through the bulktransmitter optic into a field external to the optical system accordingto an illumination pattern in which each discrete beam in theillumination pattern represents a non-overlapping field-of-view withinthe field, and a light detection system configured to detect photonsemitted from the illumination source and reflected from surfaces withinthe field, the light detection system including a bulk receiver opticand a photosensor layer formed of a two-dimensional array ofphotosensors including a first subset of photosensors positioned tocorrespond with a first light emitter of the array of light emitterssuch that a field of view of the first light emitter overlaps with atleast a portion of each field of view of each photosensor in the firstsubset of photosensors, each photosensor in the first subset ofphotosensors is configured to receive at least a portion of lightemitted from the first light emitter. The optical system also includesemitter array firing circuitry coupled to the array of light emittersand configured to execute a plurality of capture periods where, for eachcapture period the emitter array firing circuitry sequentially firessubsets of emitters within the array of light emitters according to afiring sequence until the illumination pattern is generated, and sensorarray readout circuitry coupled to the array of photosensors andconfigured to synchronize the readout of individual photosensors withinthe array concurrently with the firing of corresponding emitters withinthe array of light emitters.

In some embodiments, a light ranging device includes a semiconductoremitter array including a two-dimensional array of light emittersaligned to project discrete beams of light into a field external to theoptical system according to an illumination pattern in which eachdiscrete beam in the illumination pattern represents a non-overlappingfield-of-view within the field, the two-dimensional array of lightemitters including a plurality of emitter banks aligned side-by-side,where each emitter bank includes a subset of emitters in thetwo-dimensional array of light emitters and is independently operable toemit light from its subset of emitters, and emitter array drivingcircuitry coupled to the plurality of emitter banks, the emitter arraydriving circuitry configured to activate one emitter bank in theplurality of emitter banks at a time according to a firing sequence inwhich the subset of emitters in the activated bank are fired.

In some additional embodiments, a light ranging device includes aninterconnection structure, a semiconductor emitter array coupled to theinterconnection structure, the semiconductor emitter array including abulk transmitter optic and a two-dimensional array of light emittersaligned to project discrete beams of light through the bulk transmitteroptic into a field external to the optical system according to anillumination pattern in which each discrete beam in the illuminationpattern represents a non-overlapping field-of-view within the field, thetwo-dimensional array of light emitters including a plurality of emitterbanks aligned side-by-side, each emitter bank is independently operableto emit light, a plurality of drivers mounted directly onto a surface ofthe semiconductor emitter array and electrically coupled to the array oflight emitters, each driver configured to control the activation of arespective emitter bank according to a firing sequence, a heat sinkcoupled to a surface of the interconnection structure opposite from asurface upon which the semiconductor emitter array is coupled, the heatsink including a plurality of fins and configured to dissipate heatgenerated by the semiconductor emitter array, and a thermoelectriccooler positioned between the interconnection structure and the heatsink, the thermoelectric cooler configured to transfer heat from theinterconnection structure to the heat sink.

In certain embodiments, a light ranging device includes aninterconnection structure, an emitter array coupled to theinterconnection structure, the emitter array including a bulktransmitter optic and a two-dimensional array of light emitters alignedto project discrete beams of light through the bulk transmitter opticinto a field external to the optical system according to an illuminationpattern in which each discrete beam in the illumination patternrepresents a non-overlapping field-of-view within the field, thetwo-dimensional array of light emitters including a plurality of emitterbanks aligned side-by-side, each emitter bank being a semiconductor dieupon which a respective subset of light emitters of the array of lightemitters is constructed, a capacitor bank mounted on the interconnectionstructure and electrically coupled to the array of light emitters via afirst contact array positioned between the capacitor bank and the arrayof light emitters, the capacitor bank including a plurality ofcapacitors configured to charge and discharge its stored energy toactivate the array of light emitters to project the discrete beams oflight, each capacitor coupled to a respective emitter bank andconfigured to activate the respective subset of light emitters, aplurality of drivers mounted on the interconnection structure andelectrically coupled to the array of light emitters via a second contactarray positioned between the plurality of drivers and the array of lightemitters, each driver configured to control the activation of therespective subset of light emitters, and an electrical connector mountedon the interconnection structure and electrically coupled to theplurality of drivers, the electrical connector is configured to couplewith an external device to allow the external device to control theoperation of the light emission system.

A better understanding of the nature and advantages of embodiments ofthe present disclosure may be gained with reference to the followingdetailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary solid state electronicscanning LIDAR system, according to some embodiments of the presentdisclosure.

FIG. 2A is a simplified illustration of an emitter array and a sensorarray for an exemplary solid state electronic scanning LIDAR system,according to some embodiments of the present disclosure.

FIGS. 2B-2D are simplified diagrams illustrating an exemplary firingsequence of a emitter array and sensor readout sequence of a sensorarray, according to some embodiments of the present disclosure.

FIG. 3 is an illustrative example of the light transmission anddetection operation for an electronic scanning LIDAR system in ascenario, according to some embodiments of the present disclosure.

FIG. 4 is a simplified illustration of the overlapping field of viewsfor an emitter array and a sensor array, according to some embodimentsof the present disclosure

FIG. 5 is a simplified diagram illustrating a detailed side-view of anexemplary solid state electronic scanning LIDAR system, according tosome embodiments of the present disclosure.

FIG. 6 is a top-down, system view of an exemplary emitter driving systemfor an emitter array in a solid state electronic scanning LIDAR system,according to some embodiments of the present disclosure.

FIG. 7A is a simplified illustration of an exemplary emitter arraypaired with drivers and arranged in individually controllable banks,according to some embodiments of the present disclosure.

FIG. 7B is a simplified illustration of an exemplary emitter arraypaired with drivers and arranged in individually controllable columns,according to some embodiments of the present disclosure.

FIG. 8A is a simplified illustration of an exemplary LIDAR systemincluding a plurality of independently operable emitter arrays havingnon-overlapping fields of view, each with their own set of drivers, foremitting light that can be captured by a sensor array, according to someembodiments of the present disclosure.

FIG. 8B is a simplified illustration of a micro-lens array superimposedover a photosensor of FIG. 8A, according to some embodiments of thepresent disclosure.

FIG. 8C is a simplified cross-sectional view of the micro-lens array inFIG. 8B positioned in front of a photosensor of FIG. 8A when sensinglight from the field, according to some embodiments of the presentdisclosure.

FIG. 8D is a simplified illustration of an exemplary LIDAR systemincluding a plurality of independently operable emitter arrays havingoverlapping fields of view, each with their own set of drivers, foremitting light that can be captured by a sensor array, according to someembodiments of the present disclosure.

FIG. 8E is a simplified illustration of the overlapping field of viewsfor an emitter array and a sensor array according to the embodimentsdiscussed with respect to FIG. 8D.

FIG. 9A is a simplified illustration of an exemplary light emissionsystem that includes a one-dimensional emitter array and a MEMS device,according to some embodiments of the present disclosure.

FIG. 9B is a simplified illustration of an exemplary light emissionsystem that includes a single emitter and a MEMS device, according tosome embodiments of the present disclosure.

FIG. 10 is a simplified cross-sectional view diagram of an exemplaryenhanced light emission system, according to some embodiments of thepresent disclosure.

FIG. 11 is a simplified diagram of a sensor control system for operatingan m×n sensor array per column, according to some embodiments of thepresent disclosure.

FIG. 12 is a simplified diagram of a sensor control system for operatingan m×n sensor array per row, according to some embodiments of thepresent disclosure.

FIG. 13A is a simplified diagram of a control system for operating anm×n sensor array per photosensor with column and row control circuits,according to some embodiments of the present disclosure.

FIG. 13B is a simplified diagram of a control system for operating anm×n sensor array per photosensor with control circuits specific to eachphotosensor, according to some embodiments of the present disclosure.

FIG. 14 is a simplified illustration of a configuration where an emitterarray and a sensor array have a one-to-one correspondence, according tosome embodiments of the present disclosure.

FIG. 15 is a simplified illustration of a configuration where an emitterarray and a sensor array have a one-to-one correspondence but at amodified resolution in one dimension, according to some embodiments ofthe present disclosure.

FIG. 16 is a simplified illustration of a configuration where a sensorarray has multiplexed photosensors, according to some embodiments of thepresent disclosure.

FIG. 17 is a cross-sectional view of the construction of an exemplarylight transmission module, according to some embodiments of the presentdisclosure.

FIG. 18 is a simplified illustration of solid state electronic scanningLIDAR systems implemented at the outer regions of a road vehicle,according to some embodiments of the present disclosure.

FIG. 19 is a simplified illustration of solid state electronic scanningLIDAR systems implemented on top of a road vehicle, according to someembodiments of the present disclosure.

FIG. 20 is a simplified top-down illustration of an exemplary solidstate electronic scanning LIDAR system that includes more than one setof emission and detection systems to achieve an expanded field of view,according to some embodiments of the present disclosure.

FIG. 21A is a simplified cross-sectional view diagram of part of a lightdetection system where there is no cross-talk between channels.

FIG. 21B is a simplified cross-sectional view diagram of part of a lightdetection system where there is cross-talk between channels.

FIG. 22 is a simplified cross-sectional diagram of an exemplarymicro-optic receiver channel structure, according to some embodiments ofthe present disclosure.

FIG. 23 is a simplified cross-sectional view diagram of an exemplarysimplified receiver channel, according to some embodiments of thepresent disclosure.

FIG. 24 is a simplified drawing of a zoomed-in portion of a sensorarray, according to some embodiments of the present disclosure.

FIG. 25 is a simplified drawing of a zoomed-in portion of a sensor arraywith one or more components mounted on a backside of the substrate,according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

Some embodiments of the disclosure pertain to stationary, solid-stateLIDAR systems in which there is no spinning column or mirrorgalvanometers. Embodiments can emit light into a field external to theLIDAR system and capture the emitted light after it has reflected off anobject in the field. Embodiments of the disclosure can then use thecaptured emitted light to create a three-dimensional image of the field.Embodiments of the disclosure can have improved accuracy, reliability,size, integration and appearance as compared to currently availablespinning LIDAR systems. Additionally, embodiments of the disclosure cancapture an image at a given resolution using less power than solid-stateflash-type LIDAR systems.

A solid-state array electronic scanning LIDAR system according to someembodiments of the disclosure can include a light transmission moduleand a light sensing module. The light transmission module can include atransmitter layer that includes an array of individual emitters, and thelight sensing module can include a sensor layer that includes an arrayof photosensors. Each emitter in the emitter array can be paired with acorresponding sensor (i.e., photosensor) in the photosensor array. Insome embodiments, instead of flashing a scene with the entire set ofemitters, only a subset of emitters are activated at a time and only acorresponding subset of photosensors are read out simultaneous with thefiring of the emitters. Different subsets of emitters are then activatedat different times with corresponding subsets of photosensors being readout simultaneously so that all emitters in the emitter array can beactivated and all the photosensors in the sensor array can be readoutthrough one emission cycle.

As an example, the emitter array of a light transmission module can emitlight by activating one column at a time and in sequential order fromleft to right for each emission cycle. Likewise, the sensor array can beconfigured to sense (i.e., readout) the emitted light in a correspondingsequence. For instance, the sensor array can be configured to measurelight one column at a time and in sequential order from left to right,so that the emitter and sensor arrays operate in a synchronous manner.That way only those photosensors that correspond with the activatedemitters are read out to sense light.

In some embodiments a solid-state LIDAR system includes a micro-opticreceiver layer formed over the sensor array. The micro-optic receiverlayer can include optical elements that, combine with the sensor array,to form a two-dimensional array of micro-optic receiver channels. Eachmicro-optic receiver channel can include a photosensor from the sensorarray, an aperture from the micro-optic layer that is configured tolimit the field-of-view of its respective photosensor to match thefield-of-view of a corresponding emitter, and an optical filter from themicro-optic layer that is configured to pass incident photons at awavelength and passband that includes the operating wavelength of theemitter array. In some embodiments the micro-optic receiver layer canfurther include one or more lens layers, additional aperture layers,and/or other optical structures.

In some instances, the micro-optic receiver channel structure has acolumnar arrangement with enclosures having absorbent and/or reflectivesidewalls and/or focusing funnels. The micro-optic receiver channelmaximizes the collection of incoming rays through its aperture,collimates the light to make it perpendicular to the optical filter, andminimizes crosstalk with adjacent micro-optic receiver channels due tomixing of inputs from neighboring apertures, as will be discussed indetail below. In various instances, bulk imaging optics according to thepresent disclosure modify light or other radiation for an entire arrayof emitters or photosensors. Micro-optic structures can be included aspart of the array and can modify light differently for differentemitters and/or photosensors in the array. In some embodiments, there isone or more micro-optic elements for each individual array element(photosensor and/or emitter).

In some embodiments, the light transmission module can include amicro-optic transmitter channel array to enhance light outputted fromthe array of emitters. During operation, light outputted by the array ofemitters (e.g., laser pulses) passes through the micro-optic transmitterchannel array and enters a bulk transmitter optic having a largenumerical aperture to better capture light from the micro-optictransmitter channel array. The light then exits the bulk transmitteroptic and illuminates a plurality of spots at a distant field. Themicro-optic transmitter channel array can improve the brightness ofbeams emanating from the bulk transmitter optic to provide enhanced spotillumination, while at the same time improving the spatial resolution ofthe measured image, as will be discussed in detail further herein.

A bulk imaging optic as defined herein can be one or more opticalsurfaces, possibly including multiple lens elements, that have clearapertures greater than one millimeter and that is positioned to receivelight projected from, or focus received light on, a micro-optictransmitter/receiver layer. A bulk imaging optic that projects lightreceived from an optical emitter, such as a micro-optic transmitterlayer, is sometimes referred to herein as a bulk transmitter optic or asan output bulk imaging optic. A bulk optic layer that focuses lightreceived from a field onto an optical detector, such as a micro-opticreceiver layer, is sometimes referred to herein as a bulk receiver opticor as an input bulk imaging optic. An input, image-space telecentricbulk imaging optic allows the system to measure narrowband lightuniformly over a wide field-of-view (FOV).

According to some embodiments of the present disclosure, the lightsensing module collects light within a limited wavelength range from awide field-of-view. For example, the sensing module can capture imagesand detect light across a FOV of at least 10 degrees. In certainembodiments, the sensing module can capture images and detect lightacross a FOV of at least 20 degrees, across a FOV of at least 30degrees, and across a FOV of at least 45 degrees or at least 90 degreesin some embodiments. Furthermore, the sensing module can detect light ata narrow wavelength of approximately 10 nm or less. This is in contrastto a traditional camera which detects light across the entire visiblespectrum or into three different wide, RGB color bands, each of whichmay be 100 nm or wider. In some particular embodiments, the lightsensing module can detect light at a wavelength of approximately 5 nm orless. In some embodiments, the sensing module can detect light at awavelength of less than 5 nm across a FOV of approximately 32 degrees.The FOV can be in the vertical and/or horizontal direction, or any otherangle in between.

It is to be appreciated that electronic scanning LIDAR systems accordingto embodiments of the present disclosure can be configured and operatedin various ways, as will be discussed in further detail herein.

I. Electronic Scanning LIDAR Systems

A better understanding of a solid state electronic scanning LIDAR systemaccording to some embodiments of the disclosure can be ascertained withreference to FIG. 1.

FIG. 1 illustrates a block diagram of an exemplary solid stateelectronic scanning LIDAR system 100 according to some embodiments ofthe present disclosure. Solid state electronic scanning LIDAR system 100can include a light ranging device 102 and a user interface 150. Lightranging device 102 can include a ranging system controller 104, a lighttransmission (Tx) module 106 and a light sensing (Rx) module 108.Ranging data can be generated by light ranging device 102 bytransmitting one or more light pulses 110 from the light transmissionmodule 106 to objects in a field of view surrounding light rangingdevice 102. Reflected portions 112 of the transmitted light are thendetected by light sensing module 108 after some delay time. Based on thedelay time, the distance to the reflecting surface can be determined.Other ranging methods can be employed as well, e.g. continuous wave,photodemodulation, Doppler, and the like.

Light transmission module 106 includes an emitter array 114, which canbe a one-dimensional or two-dimensional array of emitters, and a Txoptical system 116, which when taken together with emitter array 114 canform a light emission system 138. Tx optical system 116 can include abulk transmitter optic 144 that is image-space telecentric. In someembodiments, Tx optical system 116 can further include one or more Txoptical components 146, such as an aperture layer, a collimating lenslayer and an optical filter, that can be combined with emitter array 114to form an array of micro-optic transmitter channels where eachmicro-optic transmitter channel can increase the brightness of beamsemanating from the bulk transmitter optic and/or for beam shaping, beamsteering or the like, as will be discussed further herein. Emitter array114 or the individual emitters can be laser sources, such asvertical-cavity surface-emitting lasers (VCSEL), laser diodes, and thelike. Tx module 106 can further include an optional processor 118 andmemory 120, although in some embodiments these computing resources canbe incorporated into ranging system controller 104. In some embodiments,a pulse coding technique can be used, e.g., Barker codes and the like.In such cases, memory 120 can store pulse-codes that indicate when lightshould be transmitted. In some embodiments, the pulse-codes are storedas a sequence of integers stored in memory.

Light sensing module 108 can include a sensor array 126, which can be,e.g., a two-dimensional array of photosensors. Each photosensor(sometimes referred to herein as just a “sensor” or as a “pixel”) caninclude a collection of photodetectors, e.g., SPADs or the like, or asensor can be a single photon detector (e.g., an APD). Light sensingmodule 108 includes a receiver optical sensing system 128, which whentaken together with sensor array 126 can form a light detection system136. In some embodiments, receiver optical sensing system 128 caninclude a receiver bulk receiver optic 140 and receiver opticalcomponents 142, such as an aperture layer, a lens layer and an opticalfilter, that can be combined with sensor array 126 to form an array ofmicro-optic receiver channels where each micro-optic receiver channelmeasures light that corresponds to an image pixel in a distinct field ofview of the surrounding field in which light ranging device 102 ispositioned. Further details of various examples of micro-optic receiverchannels that can be incorporated into light ranging device 102according to the present disclosure are discussed below in conjunctionwith FIGS. 22 and 23 below.

Each photosensor sensor (e.g., a collection of SPADs) of sensor array126 can correspond to a particular emitter of emitter array 114, e.g.,as a result of a geometrical configuration of light sensing module 108and Tx module 106. As mentioned herein, light ranging device 102 can bean electronic scanning LIDAR device that can capture an image of a sceneby activating only a subset of emitters at a time and by reading outonly a corresponding subset of photosensors simultaneous with the firingof the emitters. Different subsets of emitters can be activated atdifferent times with corresponding subsets of photosensors being readoutsimultaneously so that all emitters can be eventually activated and allthe photosensors in the sensor array can be readout through one emissioncycle. As an example, an emitter array can emit light by activating onecolumn at a time and in sequential order from left to right for eachemission cycle while the sensor array can be configured to readout thecorresponding photosensors in a corresponding sequence. Accordingly,embodiments of the disclosure can include one or more components tosynchronize the emitting and sensing of light.

In some embodiments, light detection system 136 can include a sensorcontroller 125 coupled to sensor array 126 and configured to control theoperation of sensor array 126. Sensor controller 125 can be any suitablecomponent or group of components capable of selecting one or morephotosensors to sense light, such as an ASIC, microcontroller, FPGA, orany other suitable processor coupled to a selecting circuit, e.g., amultiplexer. Likewise, light emission system 138 can include an emittercontroller 115 coupled to emitter array 114 and configured to controlthe operation of sensor array 126. Emitter controller 115 can also beany suitable processor mentioned above for sensor controller 125 andinclude one or more driving components for operating emitter array 114.

In some embodiments, sensor controller 125 and emitter controller 115are synchronized such that the sequence of light emissions in emitterarray 114 are synchronized with the sequence of reading out photosensorsin sensor array 126. As an example, both sensor controller 125 andemitter controller 115 can be coupled to a clock 117 so that bothcontrollers can operate based on the same timing scheme. Clock 117 canbe an electrical component that generates a specific signal thatoscillates between a high and low state at a certain speed forcoordinating actions of digital circuits. Optionally, sensor controller125 and emitter controller 115 can include their own clock circuits forcoordinating their own actions. In such embodiments, sensor controller125 and emitter controller 115 can be communicatively coupled togethervia a communication line 119 such that sensor controller 125 cansynchronize its clock with emitter controller 115. That way, sensorcontroller 125 and emitter controller 115 can operate sensor array 126and emitter array 114, respectively, in synchronization to effectuateimage capture.

In some further embodiments, instead of, or in addition to, sensorcontroller 125 and emitter controller 115, ranging system controller 104can be configured to synchronize the operation of light sensing module108 and light transmission module 106 such that the sequence of lightemissions by emitter array 114 are synchronized with the sequence ofsensing light by sensor array 126. For instance, ranging systemcontroller 104 can instruct emitter array 114 of light transmissionmodule 106 to emit light by activating one column at a time and insequential order from left to right for each emission cycle, andcorrespondingly instruct sensor array 126 in light sensing module 108 tosense light one column at a time and in the same sequential order. Insuch embodiments, ranging system controller 104 can have its own clocksignal on which it bases its sequencing instructions to light sensingmodule 108 and light transmission module 106. It is to be appreciatedthat other forms of sequencing for light detection are envisioned hereinand that such sequences are not limiting, as will be discussed furtherherein.

In some embodiments, sensor array 126 of light sensing module 108 isfabricated as part of a monolithic device on a single substrate (using,e.g., CMOS technology) that includes both an array of photosensors and aprocessor 122 and a memory 124 for signal processing the measured lightfrom the individual photosensors (or groups of photosensors) in thearray. The monolithic structure including sensor array 126, processor122, and memory 124 can be fabricated as a dedicated ASIC. In anotherembodiment, sensor array 126 can be fabricated as a stack of two or moremonolithic electronic devices (“semiconductor dies”) bonded togetherinto a single light sensing module 108 with electrical signals passingbetween them. In this embodiment, the top array of photosensors can befabricated in a process that maximizes photosensing efficiency orminimizes noise while the other dies are optimized for lower power, highspeed digital processing.

In some embodiments, optical components 142 can also be a part of themonolithic structure in which sensor array 126, processor 122, andmemory 124 are a part. For example, an aperture layer, lens layer, andan optical filter layer of optical components 142 can be stacked overand bonded with epoxy to a semiconductor substrate having multiple ASICsfabricated thereon at the wafer level before or after dicing. Forinstance, the optical filter layer can be a thin wafer that is placedagainst the photosensor layer and then bonded to the photosensor layerto bond the optical filter layer with the photosensor layer to have theoptical layer form part of the monolithic structure; the collimatinglens layer can be injection molded onto the optical filter layer; and,the aperture layer can be formed by layering a non-transparent substrateon top of a transparent substrate or by coating a transparent substratewith an opaque film. Alternatively, the photosensor layer can befabricated and diced, and the optical filter layer, collimating lenslayer, and the aperture layer can be fabricated and diced. Each dicedphotosensor layer and optical layers can then be bonded together to forma monolithic structure where each monolithic structure includes thephotosensor layer, optical filter layer, collimating lens layer, and theaperture layer. By bonding the layers to the ASIC, the ASIC and thebonded layers can form a monolithic structure. The wafer can then bediced into devices, where each device can be paired with a respectivebulk receiver optic 140 to form light sensing module 108. In yet otherembodiments, one or more components of light sensing module 108 can beexternal to the monolithic structure. For example, the aperture layermay be implemented as a separate metal sheet with pin-holes.

As mentioned above, processor 122 (e.g., a digital signal processor(DSP), microcontroller, field programmable array (FPGA), and the like)and memory 124 (e.g., SRAM) can perform signal processing of the rawhistograms from the individual photon detectors (or groups of detectors)in the array. As an example of signal processing, for each photondetector or grouping of photon detectors, memory 124 can accumulatecounts of detected photons over successive time bins, and these timebins taken together can be used to recreate a time series of thereflected light pulse (i.e., a count of photons vs. time). Thistime-series of aggregated photon counts is referred to herein as anintensity histogram (or just histogram). Processor 122 can implementmatched filters and peak detection processing to identify return signalsin time. In addition, processor 122 can accomplish certain signalprocessing techniques, such as multi-profile matched filtering to helprecover a photon time series that is less susceptible to pulse shapedistortion that can occur due to SPAD saturation and quenching. In someembodiments, all or parts of such filtering can be performed byprocessor 122.

In some embodiments, the photon time series output from processor 122are sent to ranging system controller 104 for further processing, e.g.,the data can be encoded by one or more encoders of ranging systemcontroller 104 and then sent as data packets to user interface 150.Ranging system controller 104 can be realized in multiple waysincluding, e.g., by using a programmable logic device such an FPGA, asan ASIC or part of an ASIC, using a processor 130 with memory 132, andsome combination of the above. Ranging system controller 104 can controllight sensing module 108 by sending commands that include start and stoplight detection and adjust photodetector parameters. Similarly, rangingsystem controller 104 can control light transmission module 106 bysending commands, or relaying commands that include, for example,controls to start and stop light emission and controls that can adjustother light-emitter parameters (e.g., pulse codes). In some embodiments,ranging system controller 104 has one or more wired interfaces orconnectors for exchanging data with light sensing module 108 and withlight transmission module 106. In other embodiments, ranging systemcontroller 104 communicates with light sensing module 108 and lighttransmission module 106 over a wireless interconnect such as an opticalcommunication link.

Solid state electronic scanning LIDAR system 100 can interact with auser interface 150, which can be any suitable user interface forenabling a user to interact with a computer system, e.g., a display,touch-screen, keyboard, mouse, and/or track pad for interfacing with alaptop, tablet, and/or handheld device computer system containing a CPUand memory. User interface 150 may be local to the object upon whichsolid state electronic scanning LIDAR system 100 is mounted but can alsobe a remotely operated system. For example, commands and data to/fromsolid state electronic scanning LIDAR system 100 can be routed through acellular network (LTE, etc.), a personal area network (Bluetooth,Zigbee, etc.), a local area network (WiFi, IR, etc.), or a wide areanetwork such as the Internet.

User interface 150 of hardware and software can present the imager datafrom the device to the user but can also allow a user to control solidstate electronic scanning LIDAR system 100 with one or more commands.Example commands can include commands that activate or deactivate theimager system, specify photodetector exposure level, bias, samplingduration and other operational parameters (e.g., emitted pulse patternsand signal processing), specify light emitters parameters such asbrightness. In addition, commands can allow the user to select themethod for displaying results. The user interface can display imagersystem results which can include, e.g., a single frame snapshot image, aconstantly updated video image, and/or a display of other lightmeasurements for some or all pixels.

In some embodiments, for example where LIDAR system 100 is used forvehicle navigation, user interface 150 can be a part of a vehiclecontrol unit that receives output from, and otherwise communicates withlight ranging device 102 and/or user interface 150 through a network,such as one of the wired or wireless networks described above. One ormore parameters associated with control of a vehicle can be modified bythe vehicle control unit based on the received LIDAR data. For example,in a fully autonomous vehicle, LIDAR system 100 can provide a real time3D image of the environment surrounding the car to aid in navigation inconjunction with GPS and other data. In other cases, LIDAR system 100can be employed as part of an advanced driver-assistance system (ADAS)or as part of a safety system that, e.g., can provide 3D image data toany number of different systems, e.g., adaptive cruise control,automatic parking, driver drowsiness monitoring, blind spot monitoring,collision avoidance systems, etc. When user interface 150 is implementedas part of a vehicle control unit, alerts can be provided to a driver ortracking of a proximity of an object can be tracked.

As mentioned above, some embodiments of the disclosure pertain to asolid-state LIDAR system that includes an electronically scanningtransmitting element and an electronically scanning receiving element.FIG. 2A is a simplified illustration of an emitter array 210 and sensorarray 220 for an exemplary solid state electronic scanning LIDAR system200, according to some embodiments of the present disclosure. Emitterarray 210 can be configured as a two-dimensional m×n array of emitters212 having m number of columns and n number of rows. In someembodiments, sensor array 220 can be configured to correspond withemitter array 210 such that each photosensor 222 is mapped to arespective emitter 212 in emitter array 210. Thus, sensor array 220 canbe configured as a corresponding two-dimensional m×n array ofphotosensors 222. In some embodiments, emitter array 210 and sensorarray 220 are generally large arrays that include more elements (i.e.,more emitters and more photosensors) than emitter or sensor arraystypically employed in rotating LIDAR systems. The size, i.e., overallphysical dimensions, of sensor array 220 (and thus the correspondingemitter array 210 for illuminating the field of view corresponding tosensor array 220 as well) along with the pitch of the photosensorswithin sensor array 220 can dictate the field of view and the resolutionof images capable of being captured by sensor array 220. Larger sizedarrays generally result in larger fields of view, and smaller pitchsizes generally result in captured images with higher resolution. Insome embodiments, emitter array 210 and sensor array 220 are each formedfrom a single semiconductor die while in other embodiments, one or bothof emitter array 210 and sensor array 220 can be formed of multiplechips mounted to a common substrate as discussed herein with respect toFIG. 6.

FIGS. 2B-2D are simplified diagrams illustrating a firing sequence ofemitter array 210 and sensor readout sequence of sensor array 220,according to some embodiments of the present disclosure. As shown inFIG. 2B, a first stage of an image capturing sequence can start byfiring emitter column 214(1) of emitter array 210 and simultaneouslyreading out sensor column 224(1) of sensor array 220. During this firststage, a pulse of light emitted from each individual emitter in column214(1) is emitted into a field. The emitted light can then be reflectedoff of one or more objects in the field and be captured by a respectivesubset of photosensors within sensor column 224(1) of sensor array 220.Next, during a second stage of the sequence, emitters from a secondcolumn 214(2) of the emitter array can be activated to emit a pulse oflight that can be read out by the sensors in column 224(2) in the sensorarray as shown in FIG. 2C. The sequential firing of columns of emittersand simultaneous reading out of photosensors in a corresponding columnof photosensors continues until the last column of emitters 214(m) isactivated concurrently with the last column of photosensors 224(m) beingread as shown in FIG. 2D. When one full cycle is complete (m stages ofthe image capturing sequence), every column of emitter array 210 willhave been activated and every column of sensor array 220 will have beenreadout to detect photons emitted from the corresponding columns ofemitter array 210. The cycle can then be continuously repeated whileLIDAR system 200 is in operation.

While FIGS. 2B-2D illustrate an image capturing sequence in which firedemitters are advanced one column per stage, embodiments of thedisclosure are not limited to any particular sequence. For example, insome embodiments the following sequence can be employed: for stage one,a first column of emitter array 210 is fired; for stage 2, column(m/2+1) is fired; for stage 3, column 2 is fired, for stage 4, column(m/2+2) is fired, etc. until the m^(th) stage when column m is fired.Such an embodiment can be beneficial in minimizing cross-talk within thesensor array as adjacent sensor columns are not readout in successivestages. As another example, two or more adjacent columns of emitters canbe fired concurrently while the corresponding two or more adjacentcolumns of sensors are read out. As an illustration where four columnsare fired and read simultaneously, during a first stage of an imagecapturing sequence, columns 1-4 of emitter array 210 can be fired,during a second stage columns 5-8 can be fired, etc. These examples arejust a few of the many different firing and readout sequences that arepossible and other firing and readout sequences are possible in otherembodiments.

As an example, instead of operating by column where a column of emittersare fired while simultaneously reading a corresponding column ofphotosensors, embodiments can operate by row where a row of emitters arefired while simultaneously reading a corresponding row of photosensors.In some further embodiments, LIDAR systems can operate by emitter whereindividual or groups of emitters can be fired while simultaneouslyreading a corresponding photosensor or groups of photosensors. In suchembodiments, each emitter can be individually addressable with suitableemitter-specific driving circuitry so that embodiments can operate tofire arbitrary groupings of emitters that match the groupings shown inFIGS. 13A and 13B. It is to be appreciated that any specific firingarrangement of emitters can have a corresponding reading arrangement ofphotosensors, according to some embodiments of the present disclosure.

FIG. 3 is an illustrative example of the light transmission anddetection operation for an electronic scanning LIDAR system in ascenario 300, according to some embodiments of the present disclosure.Specifically, FIG. 3 shows solid state electronic scanning LIDAR system200 collecting three-dimensional distance data of a volume or scene thatsurrounds the system. FIG. 3 is an idealized drawing to highlightrelationships between emitters and sensors, and thus other componentsare not shown.

As discussed in FIG. 2A, electronic scanning LIDAR system 200 includesan emitter array 210 and a sensor array 220. Emitter array 210 can be anarray of light emitters, e.g. an array of vertical-cavitysurface-emitting lasers (VCSELs) and the like, that includes columns ofemitters 302 and 304. Sensor array 220 can be an array of photosensorsthat includes columns of sensors 306 and 308. The photosensors can bepixelated light sensors that employ, for each photosensor, a set ofdiscrete photodetectors such as single photon avalanche diodes (SPADs)and the like. However, various embodiments can deploy other types ofphoton sensors.

Each emitter can be spaced apart from its neighbor by a pitch distanceand can be configured to transmit light pulses into a different field ofview from its neighboring emitters, thereby illuminating a respectivefield of view associated with only that emitter. For example, column ofemitters 302 emits illuminating beams 310 (each formed from one or morelight pulses) into region 312 of the field of view and thus reflect offof a tree 313 in the field. Likewise, column of emitters 304 emitsilluminating beams 314 into region 316 of the field of view. It is to beappreciated that in the embodiment shown in FIG. 3, emitter array 210scans through its columns in sequential order from left to right. Thus,FIG. 3 shows the first instance of time where column of emitters 302 isbeing activated and the last instance of time where the last column,i.e., column of emitters 304, is activated. The other columns cansequentially step from left to right between column 302 and 304. WhileFIG. 3 shows an embodiment where emitter and sensor arrays 210 and 220operate by column and in sequential order, embodiments are not limitedto such configurations. In other embodiments, emitter and sensor arrays210 and 220 can operate by column in a non-sequential order to minimizecross-talk, or by row in a sequential or non-sequential order tominimize crosstalk, or any other suitable order for emitting andreceiving light, as will be discussed above and in detail furtherherein. It is also to be appreciated that columns of emitters 302 and304 and columns of sensors 306 and 308 can be representative of onlyportions of much larger columns of emitter array 210 and sensor array220, respectively, for ease of discussion. Thus, while FIG. 3 only showsemitters and sensors for 21 distinct points for ease of illustration, itcan be understood that other implementations can have significantlymore. That is, a denser sampling of points can be achieved by having adenser array of emitters and a corresponding denser array ofphotosensors.

Each field of view that is illuminated by an emitter can be thought ofas a pixel or spot in the corresponding 3D image that is produced fromthe ranging data. Thus, each emitter can be distinct from other emittersand be non-overlapping with other emitters such that there is aone-to-one mapping between the set of emitters and the set ofnon-overlapping fields of view. In some embodiments, emitter array 210and sensor array 220 are each solid state devices that can be very smalland very close to each other. For instance, the size of an emitter orsensor array, according to the present embodiments, could range from afew millimeters to a few centimeters.

As such, the dimensions of the two arrays and their separation distance,which can be approximately 1 cm, are negligible compared with thedistances to the objects in the scene. When this arrangement of emitterand sensor arrays is paired with respective bulk optics that cancollimate the light emitted by the emitter array and focus the reflectedlight into the sensor array, the sensor array and emitter array can havesignificantly similar fields of view beyond a threshold distance suchthat each emitter and corresponding sensor looks at essentially the samespot in the field. This concept can be better understood with referenceto FIG. 4.

FIG. 4 is a simplified illustration of the overlapping field of viewsfor emitter array 210 and sensor array 220, according to someembodiments of the present disclosure. Each emitter in emitter array 210can emit a pulse of light that is shown in FIG. 4 as a cone 402 thatgets collimated through a bulk transmitter optic 404 and outputted intothe field as emitted light 406. Emitted light 406 can then reflect offof one or more objects in the field and propagate back toward sensorarray 220 as reflected light 412 that first propagates through bulkreceiver optic 410, which focuses reflected light 412 back down into afocal point as a cone of pulsed light 408 and then onto a correspondingphotosensor within sensor array 220. As can be understood with referenceto FIG. 4, the distance between bulk transmitter and receiver optics 404and 410, which can range between 1-3 cm, is relatively small comparedwith the distance to the scene. Thus, as the scene gets farther, thefield of view for the emitter array increasingly overlaps with the fieldof view for the sensor array. For instance, as shown in FIG. 4,overlapping regions 414, 416, and 418 of the fields of view for emitterarray 210 and sensor array 220 get larger as the distance to the sceneincreases. Thus, at distances near the end of the scene, e.g., objectsin the field, the field of view of emitter array 210 can substantiallyoverlap the field of view of sensor array 220. Accordingly, eachcorresponding emitter and sensor can observe essentially the same pointin the scene even though the bulk receiver and transmitter optics areseparated by one or more centimeters. That is, each illuminating beamprojected from bulk transmitter optic 404 into the field ahead of thesystem can be substantially the same size and geometry as the field ofview of a corresponding photosensor (or a micro-optic receiver channelfor the corresponding photosensor) at a distance from the system. Insome embodiments, emitter array 210 can selectively project illuminatingbeams into the field ahead of system 200 according to an illuminationpattern that substantially matches, in size and geometry across a rangeof distances from system 200, the fields of view of the input channels.By having substantially overlapping field of views between the emitterarray and sensor array, solid state electronic scanning LIDAR system 200can achieve a high signal-to-noise ratio (SNR).

In some embodiments, the transmitter array and sensor array havematching geometries and the bulk optics of the emitter array aresubstantially identical to the bulk optics of the sensor array. In otherembodiments the dimensions and the bulk optics of sensor array 220 maynot be identical to those of emitter array 210, however, they can bechosen such that corresponding columns of emitter array 210 and sensorarray 220 have significantly the same field of view. For example, thesize of sensor array 220 could be larger than that of emitter array 210.This would imply that bulk receiver optics 410 of sensor array 220should be different than bulk transmitter optics 404 of emitter array210, and the two bulk optics should be carefully chosen such that thefield of view of corresponding columns in the two arrays aresignificantly the same. For instance, a similar bulk optics with lenselements that are twice as large as those of emitter array 210 could beused. The resulting bulk receiver optics would have a focal length twiceas long as the focal length of the bulk transmitter optics. In thiscase, sensor array 220 should be twice as tall and twice as wide asemitter array 210 with receiving aperture diameters twice that of theemitting diameters, ensuring that the angular field of view for everyphotosensor and emitter match.

To ensure that the corresponding columns of emitter array 210 and sensorarray 220 see the same field of view, a careful alignment process ofLIDAR system 200 can be performed before field use, e.g., by themanufacturer. Design features of some embodiments of the disclosure(e.g, having a single semiconductor die or multichip module for theemitter array and a single semiconductor die of multichip module for thesensor array) allows this alignment to be performed only once by themanufacturer, thereby easing the way at which LIDAR system 200 ismanufactured and maintained after manufacturing. During the alignment ofthe optics, one measures the field of view of every pixel and everyemitter to ensure they are significantly identical. The alignmentincludes accounting for lens properties such as aberration, distortion,and focal length as well as adjusting position and orientation of lenselements with respect to external components.

Because the fields of view of the emitters are overlapped with thefields of view of their respective sensors, each photosensor ideally candetect the reflected illumination beam that originates from itscorresponding emitter with ideally no cross-talk, i.e., no reflectedlight from other illuminating beams is detected. For example, withreference back to FIG. 3, column of emitters 302 emits illuminatingbeams 310 into region 312 of the field of view and some of theilluminating beams reflect from object 313, i.e., a tree. Ideally, areflected column of light 318 is detected by column of photosensors 306only. Thus, column of emitters 302 and column of photosensors 306 sharethe same field of view. Likewise, column of emitters 304 and column ofphotosensors 308 can also share the same field of view. For instance,during the last iteration of the emitting cycle, column of emitters 304emits illuminating beams 314 into region 316 of the field of view andsome of the illuminating beam reflects from object 315, i.e., a carparked next to object 313. In one cycle, solid state electronic scanningLIDAR system 200 in FIG. 3 can capture and generate an imagerepresenting the scene including portions of tree 313 and car 315.Additional cycles can further capture other regions of the scene,especially if system 200 is moving, such as when system 200 is mountedon a car, as will be discussed further herein with respect to FIGS.18A-18B. While the corresponding emitters and sensors are shown in FIG.3 as being in the same relative locations in their respective array, anyemitter can be paired with any sensor depending on the design of theoptics used in the system.

During a ranging measurement, the reflected light from the differentfields of view distributed around the volume surrounding the LIDARsystem is collected by the various sensors and processed, resulting inrange information for any objects in each respective field of view. Asdescribed above, a time-of-flight technique can be used in which thelight emitters emit precisely timed pulses, and the reflections of thepulses are detected by the respective sensors after some elapsed time.The elapsed time between emission and detection and the known speed oflight is then used to compute the distance to the reflecting surface. Insome embodiments, additional information can be obtained by the sensorto determine other properties of the reflecting surface in addition tothe range. For example, the Doppler shift of a pulse can be measured bythe sensor and used to compute the relative velocity between the sensorand the reflecting surface. The pulse strength can be used to estimatethe target reflectivity, and the pulse shape can be used to determine ifthe target is a hard or diffuse material.

According to some embodiments, LIDAR system 200 can transmit multiplepulses of light. In some embodiments, each coded-pulse has an embeddedpositive-valued pulse-code formed by the light intensity. The system candetermine the temporal position and/or amplitude of optical pulses inthe presence of background light by creating an intensity histogram ofdetected, reflected light at different time bins. For each time bin, thesystem adds a weighted value to the intensity histogram that depends onthe intensity of detected light. The weighted values can be positive ornegative and have varying magnitudes.

By selecting different combinations of positive-valued pulse-codes andapplying different weights, the system can detect positive-valued andnegative-valued codes suitable for standard digital signal processingalgorithms. This approach gives a high signal-to-noise ratio whilemaintaining a low uncertainty in the measured temporal position of thereflected light pulses.

II. Construction and Configuration of Solid State Electronic ScanningLIDAR Systems

FIG. 5 is a simplified diagram illustrating a detailed side-view of anexemplary solid state electronic scanning LIDAR system 500, according tosome embodiments of the present disclosure. Solid state electronicscanning LIDAR system 500 can include a light detection system 501 and alight emission system 503. Light emission system 503 provides activeillumination of at least a portion of a field in which system 500 ispositioned with narrowband light rays 505. Light detection system 501detects the narrowband light emitted from the light emission system 503after it has been reflected by objects in the field as reflected lightrays 506.

A. Light Detection System

Light detection system 501 can be representative of light detectionsystem 136 discussed above with respect to FIG. 1. Light detectionsystem 501 can include an optical sensing system and a sensor array. Theoptical sensing system can include bulk receiver optics, an aperturelayer, a collimating lens layer, and an optical filter layer; and thesensor array can include an array of photosensors, where eachphotosensor can include one or more photodetectors for measuring light.According to some embodiments, these components operate together toreceive light from a field. For instance, light detection system 501 caninclude a bulk receiver optic 502 and a micro-optic receiver (Rx) layer504. During operation, light rays 506 enter bulk receiver optic 502 frommultiple directions and gets focused by bulk receiver optic 502 to formlight cones 508. Micro-optic receiver layer 504 is positioned so thatapertures 510 coincide with the focal plane of bulk receiver optic 502.In some embodiments, micro-optic receiver layer 504 can be aone-dimensional or two-dimensional array of micro-optic receiverchannels 512, where each micro-optic receiver channel 512 is formed of arespective aperture 510, collimating lens 514, and photosensor 516positioned along the same axis in the direction of light transmission,e.g., horizontal from left to right as shown in FIG. 5. Furthermore,each micro-optic receiver channel 512 can be configured various ways tomitigate interference from stray light between photosensors, as will bediscussed further herein. During operation, each micro-optic receiverchannel 512 measures light information for a different pixel (i.e.,position in the field).

At the focal point of bulk receiver optic 502, light rays 506 focus andpass through apertures 510 in an aperture layer 511 and into respectivecollimating lenses 514. Each collimating lens 514 collimates thereceived light so that the light rays all enter the optical filter atapproximately the same angle, e.g., parallel to one another. Theaperture and focal length of bulk receiver optic 502 determine the coneangle of respective light rays that come to a focus at aperture 510. Theaperture size and the focal length of collimating lenses 514 determinehow well-collimated the admitted rays can be, which determines hownarrow of a bandpass can be implemented in optical filter 518. Theaperture layer can serve various functions during the operation of lightdetection system 500. For instance, (1) apertures 510 can constrain thepixel field of view so it has tight spatial selectivity despite a largepitch at the photosensor plane, (2) apertures 510 can constrain thefield of view to be similar or equal in size to the emitter field ofview for efficient use of emitter light, (3) the apertures can provide asmall point-like source at the collimating lens's focal plane to achievetight collimation of rays before passing through the filter, wherebetter collimation results in a tighter band that can pass through thefilter, and (4) the stop region of the aperture layer surrounding eachaperture can reject stray light. In some embodiments, collimating lenses514 are not included, and the bandpass filter passband is less narrow.

Optical filter 518 blocks unwanted wavelengths of light.Interference-based filters tend to exhibit strong angle dependence intheir performance. For example, a 1 nm wide bandpass filter with acenter wavelength (CWL) of 900 nm at a zero-degree angle of incidencemight have a CWL of 898 nm at a fifteen-degree angle of incidence.Imaging systems typically use filters several tens of nanometers wide toaccommodate this effect, so that the shift in CWL is much smaller thanthe bandpass width. However, the use of micro-optic layer 504 allows allrays to enter optical filter 518 at approximately the same angle ofincidence, thus minimizing the shift in CWL and allowing very tightfilters (e.g. less than 10 nm wide) to be used. Photosensor 516generates electrical currents or voltages in response to incidentphotons. In some embodiments, optical filter 518 is uniform across theentire array of micro-optic receiver channels 512 so that eachindividual micro-optic receiver channel 512 in the array receives thesame range of wavelengths of light.

In some embodiments, photosensors 516 are positioned on a side oppositeof collimating lenses 514 so that light rays 506 first pass throughcollimating lenses 514 and optical filter 518 before exposing onphotosensors 516. Each photosensor 516 can be a plurality ofphotodetectors, such as a mini-array of multiple single-photon avalanchedetectors (SPADs). An array of mini-arrays of SPADs can be fabricated ona single monolithic chip, thereby simplifying fabrication. In somealternative embodiments, each photosensor 516 can be a singlephotodetector, e.g., a standard photodiode, an avalanche photodiode, aresonant cavity photodiode, or another type of photodetector.

B. Light Emission System

Light emission system 503 can include a bulk transmitter optic 520 and alight emitting layer 522 formed of a one- or two-dimensional array oflight emitters 524. Each light emitter 524 can be configured to generatediscrete beams of narrowband light. In some embodiments, light emittinglayer 522 is configured to selectively project the discrete beams oflight through bulk transmitter optic 520 according to an illuminationpattern that matches, in size and geometry across a range of distancesfrom light emission system 503, the fields of view of the receiverchannels in micro-optic receiver layer 504. Light emitters 524 can beany suitable light emitting device, such as a vertical-cavitysurface-emitting lasers (VCSELS) integrated on one or more monolithicchip, or any other type of laser diode. Light emitters 524 can producecones of narrowband light 526 that are directed to bulk transmitteroptic 520, which can collimate cones of light 526 and then output thecollimated light to distant targets in the field as emitted light rays505. In some embodiments, bulk transmitter optic 520 is image-spacetelecentric.

As is evident from the illustration of parallel light rays 505 and 506in FIG. 5, each micro-optic receiver channel 512 has a non-overlappingfield of view beyond a threshold distance. As shown in FIG. 5, eachmicro-optic receiver channel 512 includes an aperture from the pluralityof apertures, a lens from the plurality of lenses, and a photodetectorfrom the plurality of photodetectors, where the aperture of each channeldefines a discrete field of view for the pixel in the channel that isnon-overlapping beyond a threshold distance within the fields of view ofthe other micro-optic receiver channels. That way, each micro-opticreceiver channel receives reflected light corresponding to a discreteposition in the field that is not measured by any other micro-opticreceiver channel in micro-optic receiver layer 504.

In additional and alternative embodiments, light rays 505 from lightcones 526 are focused on an intermediate plane in space by a micro-optictransmitter layer (not shown) before being directed to distant targetsby the bulk transmitter optic 520 to enhance the brightness andintensity of light emitted from light emission system 503. In suchembodiments, embodiments, light emission system 503 and light detectionsystem 501 are configured such that each micro-optic transmitter channel(not shown) is paired with a corresponding micro-optic receiver layer504 and the centers of their fields-of-view are aligned to beoverlapping at a certain distance from the sensor or their chief raysare made parallel. In further additional and alternative embodiments,the far-field beams of light emitted by light emission system 503 are ofsimilar size and divergence angle to the far-field fields-of-view ofeach micro-optic receiver layer 504. Details of light emission systems503 having the micro-optic transmitter layer for enhancing brightnessand intensity of outputted light will be discussed in detail below.

1. Driving Systems for Electronic Scanning LIDAR Systems

In some embodiments, an emitter array can be operated by a drivingsystem that includes various capacitors and control chips for operatingthe emitter array. FIG. 6 is a top-down, system view of an exemplaryemitter driving system 600 for an emitter array 601 in a solid stateelectronic scanning LIDAR system according to some embodiments of thepresent disclosure. Emitter array 601 can include a plurality of lightemitters 602 that are arranged in an m×n array that generates anillumination pattern. Emitter array 601 can be representative, forexample, of emitter array 210 discussed above with respect to FIGS.2A-2D and can be paired in a LIDAR system with a photosensor array suchas one of the photosensor arrays described herein that can berepresentative of sensor array 220 and includes a sensing pattern thathas a geometry matching that of the illumination pattern. Emitter array601 can be divided into a plurality of separately driven emitter banks604 a-f that are precisely aligned to form the m×n array.

In some embodiments, emitter array 601, including each of emitter banks604 a-604 f, can be formed on a single semiconductor die (e.g., a largesingle chip VCSEL array). Each bank can be driven by separate drivercircuitry 612, 614 such that there are k driver circuits for an emitterarray having k banks. Each driver circuit 612, 614 is coupled to itsrespective bank and can fire all the individual emitters 602 in its banksimultaneously. The drivers 612, 614 can be activated according to apredetermined sequence by control circuitry as discussed herein suchthat each bank is fired during an image capture period one or more timeswhile one or more columns (or other arrangements of individualphotosensors) that correspond to emitters within a given bank beingfired are readout (e.g., according to one or more of the scanningsequences similar to those discussed above with respect to FIGS. 2B-2D)until the entire photosensor array is readout. This embodiment savespower as compared to a flash LIDAR system that activates all emitters atonce.

For instance, as shown in FIG. 6, bank 604 a can be driven by respectivedrivers 612 and 614 to emit light. When driven during an emission cycle,all four columns in bank 604 a can simultaneously emit light while onlyone column of photosensors corresponding to one of the four columns ofemitters is being readout. As an example, the column of photosensorsthat is being read out can correspond to the left most column, e.g.,column 1 in bank 604 a (when interpreting the four columns in each bank604 a-f to be columns 1-4 in order from left to right). Thus, during afull emission cycle, columns 1-4 in bank 604 a can be driven whilephotosensors corresponding to column 1 of bank 604 a is being read outat a first image capture period, columns 1-4 in bank 604 b can then bedriven while photosensors corresponding to column 1 of bank 604 b isbeing read out at a second image capture period, so on and so forth forbanks 604 c-f until bank 604 a is activated again to emit columns 1-4,at which point photosensors corresponding to column 2 of bank 604 a canbe read out at a seventh image capture period. This sequence maycontinue until all of the photosensors have been read out. In thisexample, for one full emission cycle, each emitter bank can be activatedfour times, one time for each column of photosensors at each respectiveimage capture period.

In some alternative embodiments, an emission cycle may drive all fourcolumns in each bank while also simultaneously capturing data on allfour corresponding columns of photosensors in the receiver array. Forinstance bank 604 a may emit light while the corresponding columns 1through 4 of the corresponding bank of photosensors may all be enabledand read out at a first image capture period before moving on to thenext bank to repeat the sequence. This approach has the benefit of notwasting laser energy by firing a laser that does not have itscorresponding photosensor enabled to detect the reflected light.

In some embodiments each bank 604 a-604 f can be constructed as aseparate semiconductor die divided by separation regions 606. Separationregions 606 can be any suitable electrical divider to electricallyisolate neighboring banks of emitters from one another such as air gaps.By separating emitter array 601 into different banks with separationregions 606, each bank can be electrically isolated from one another andcan form discrete circuits that are individually addressable foremitting light during operation of electronic scanning LIDAR systems. Insome embodiments, emitter banks 604 a-f can be mounted on a supportstructure 605, which can be any suitable component configured to providestructural support for emitter banks 604 a-f. As an example, supportstructure 605 can be a component that is substantially flat for ensuringthat emitter banks 604 a-f are also substantially flat and positioned onthe same plane. Additionally, support structure 605 can be a highlythermally conductive material so that heat generated by the activationof emitters 602 can be quickly dissipated to avoid overheating anddamage. In some embodiments, support structure 605 is a ceramicsubstrate.

In order to generate light, current is driven through emitters 602 inemitter array 601. Thus, emitter banks 604 a-f can be coupled to acapacitor bank 608 that includes a plurality of capacitors configured todischarge current through emitter array 601. Each bank 604 a-f caninclude a respective contact array or via array 610 a-f for couplingwith capacitor bank 608. Contact arrays 610 a-f can be part of thesemiconductor dies upon which respective emitter banks 604 a-f areconstructed. In some embodiments, contact arrays 610 a-f are positionedbetween capacitor bank 608 and light emitters 602 within theirrespective emitter banks 604 a-f. Before activation of one or moreemitters in emitter array 601, one or more capacitors in capacitor bank608 can be charged so that during activation of the one or more emittersin emitter array 601, the one or more charged capacitors can bedischarged to drive current through the one or more emitters to emitnarrowband light. In some embodiments, the capacitors in capacitor bank608 can be coupled to a power source (not shown) for charging thecapacitors. The power source can be coupled to capacitor bank 608 via anarray of electrical connections 618, where each electrical connection isa via coupled to a trace (not shown) routed to the power source. Theelectrical connections and traces can be part of, or formed on, aninterconnection structure 622, e.g., a printed circuit board (PCB), uponwhich capacitor bank 608 and emitter array 601 are mounted. Each pair ofelectrical connections can be associated with positive and negativeterminals of a respective capacitor in capacitor bank 608. The traces,capacitors, emitters and drivers can be positioned so as to minimize theloop inductance of the discharge path of the circuit to minimize risetimes for the drive current in the circuit.

In some embodiments, driving system 600 can be implemented as amultichip module in which electrical inputs and outputs to the system(e.g., timing signals to drivers 612 and 614) can be transmitted to andfrom driving system 600 by an electrical connector 616 (e.g., aboard-to-board connector). In such instances, electrical connector 616can be coupled to drivers 612 and 614 to enable the transfer ofcommunication signals between them. Drivers 612 and/or 614 can besemiconductor devices, e.g., field effect transistors (FET), FPGAs,ASICs, and the like, that manage the flow of current through emitterarray 601. Thus, drivers 612 and 614 can control the order in whichemitter array 601 emits light or enable a processing system (not shown)to do so through connector 616. For instance, drivers 612 and 614 canactivate emitter array 601 by emitter bank and in sequential order fromleft to right, or vice versa. Accordingly, in one emission cycle,drivers 612 and 614 can operate emitter array 601 by activating emitters602 in emitter bank 604 a during a first instance of time, activatingemitters 602 in emitter bank 604 b during a second instance of time, andso on and so forth until the last emitter bank 604 f is activated duringa last instance of time, where the emitting of light during the firstthrough the last instances of time together form a single emissioncycle. In some embodiments, drivers 612 and 614 are coupled together viaelectrical connections 624, which can be a traces plated oninterconnection structure 622. That way drivers 612 and 614 cancommunicate with one another to control the operation of emitter array601.

As shown in FIG. 6, each bank 604 a-f can include a respective contactarray 611 a-f for coupling with driver 612. Like contact arrays 610 a-fcontact arrays 611 a-f can be part of the semiconductor dies upon whichrespective emitter banks 604 a-f are constructed. In some embodiments,contact arrays 611 a-f are positioned between drivers 612 and lightemitters 602 within their respective emitter banks 604 a-f. It is to beappreciated that reference numerals for contact arrays 611 b-611 e arenot shown in FIG. 6 to avoid cluttering the illustration withsuperimposed reference numerals. Furthermore, drivers 612 can each becoupled to a respective set of electrical connections 620, that, likeelectrical connections 618, can be a part of, or formed on,interconnection structure 622, upon which drivers 612 and 614 aremounted. Electrical connections 620 can couple drivers 612 to the powersource or any other electrical component (not shown) on interconnectionstructure 622.

2. Configurations of Emitter Arrays for Light Emission Systems

Although FIG. 6 illustrates emitter array 601 as divided into sixdifferent banks 604 a-f, embodiments are not limited to suchconfigurations and that other embodiments can have more or less than sixbanks and more or less emitters per bank. That is, emitter array 601 canbe formed of a single large bank of emitters, or emitter array 601 canbe divided into 16, 32, 64, 128, or any other number of banks, each withany number of emitter columns, without departing from the spirit andscope of the present disclosure.

For instance, FIG. 7A is a simplified illustration of an exemplaryemitter array 700 paired with drivers 702 and arranged in individuallycontrollable banks, according to some embodiments of the presentdisclosure. Emitter array 700 can be an m×n array of light emitters thatare divided into k number of individually controllable emitter banks,where k is less than n. For instance, each bank can be configured tohave four columns of light emitters so that the number of banks is aquarter of the number of columns n. Each driver 702 can activate emitterarray 700 by bank and in any order, such as left to right, right toleft, every other bank, etc. An advantage of such embodiments is thatthe drive circuitry is simplified, thereby simplifying design andmanufacturability. Additionally, separating the emitter array intomultiple banks with separate drive circuitry allows for each channel inthe system to operate at substantially lower current due to the fewernumber of emitters that are driven by each drive circuitry when comparedto flash LIDAR systems where a single drive circuitry is used to powerthe entire emitter array. This may allow the emitters in each channel tobe driven more powerfully, or for different types of drive circuits tobe employed that might not have been capable of supplying the peakcurrent required for the entire array firing at once. Furthermore, drivecircuitry can be separated from the light emitters, thereby enablingmodular manufacturing through commercially available components.

In another example, FIG. 7B is a simplified illustration of an exemplaryemitter array 701 paired with drivers 704 and arranged in individuallycontrollable columns, according to some embodiments of the presentdisclosure. Emitter array 701 can be an m×n array of light emitters thatare divided into n number of individually controllable emitter banks(e.g., twenty four banks as illustrated in FIG. 7B) so that each bankhas a single column of emitters. In this embodiment, each driver 704corresponds to one emitter bank and the set of drivers 704 can operatein conjunction with multiplexer 706 to activate individual banks withinthe emitter array in any order, such as left to right, right to left,every other bank, etc. That is, multiplexer 706 can select which columnto activate by driver 704. An advantage of such embodiments is that thesplitting of emitter array 701 into individual columns allows formodulation of columns in an interlaced way to minimize cross-talk fromstray light emitting into neighboring sensor arrays and/or to improvescanning speed. For instance, drivers 704 can activate all the evenbanks (i.e., columns) at a first instance, and then all the odd banks ata second instance, thereby completing one cycle with two iterations.Because every other column is emitted at once, only those columns ofphotosensors corresponding to the activated columns need to be operatedto measure the emitted light, thereby minimizing the chances ofcross-talk between columns of photosensors. The concept of interlacingthe modulation of columns can be extended to other interlacing schemes,such as emitting every third emitter column or fourth emitter column,which can minimize cross-talk between the next two or three neighboringcolumns of photosensors.

As shown in FIG. 7B, drivers 704 (as well as drivers 702 shown in FIG.7A) can be tightly integrated with the emitter array by, for example,directly mounting drivers 704 to a chip substrate that contains thelight emitters. This configuration can save space and help minimize thesize of the overall design. However, in some other embodiments, drivers704 can be positioned off of the chip substrate that contains the lightemitters to provide more space for additional emitters, therebyincreasing image resolution. In some embodiments, drivers 704 (anddrivers 702) can be implemented as part of a separate, driver chip ASIC,while in other embodiments, drivers 704 can be discrete componentsmounted on a ceramic or other die.

As can be appreciated by embodiments herein, the number of pixels thatis fired by a single driver dictates the amount of current that needs tobe provided by the driver. For instance, each bank in emitter array 700of FIG. 7A includes four times the number of light emitters as each bankin emitter array 701 of FIG. 7B. Thus, each driver 702 in FIG. 7A needsto provide at least four times the amount of current than that of driver704 in FIG. 7B. The difficulties associated with requiring drivers tooutput large amounts of current can sometimes offset the benefits ofsimplicity in manufacturing and design often associated with having asingle driver for activating large numbers of emitters. Someembodiments, however, can take advantage of the benefits provided byboth emitter array configurations in FIGS. 7A and 7B by using multipleemitter arrays with multiple drive systems, as discussed herein withrespect to FIGS. 8A and 8B. Additionally, photosensor arrays thatinclude an array of SPADs for each photosensor are inherently limited intheir resolution due to the number of SPADs that are typically used perpixel to increase dynamic range as well as the inclusion of guard ringsand other features in HVCMOS processes that present challenges to SPADminiaturization. As a result, some embodiments of the disclosure employother methods to increase sensor resolution. Namely, methods that employfield-of-view selectivity of the transmitter array instead of thereceiver array. For example, some embodiments of the disclosure use aVCSEL array as a transmitter array. VCSEL arrays are not constrained bysize limitations to the same degree as a SPAD-based sensor array and canbe employed, for example as described with respect to FIGS. 8A-8C, insome embodiments to achieve higher spatial resolutions than the rawpixel resolution of a detector.

FIG. 8A is a simplified illustration of an exemplary LIDAR system 800including a plurality of independently operable emitter arrays 802 a-802d having non-overlapping fields of view, each with their own set ofdrivers 804 a-d, for emitting light that can be captured by a sensorarray 806, according to some embodiments of the present disclosure. Eachemitter array 802 a-802 d can include an m×n array of emitters asdescribed in various embodiments above with the arrays being directed todifferent, respective fields of view in the far field. For example, asshown in FIG. 8A, the column 1, row 1 of emitter array 802 a is emitter812; the column 1, row 1 of emitter array 802 b is emitter 814; thecolumn 1, row 1 of emitter array 802 c is emitter 816; and the column 1,row 1 of emitter array 802 d is emitter 818. Each of emitters 812, 814,816 and 818 can be aligned to project into a distinct discretefield-of-view beyond a threshold distance.

Sensor array 806 can include an array of photosensors 808 arranged inthe same m×n configuration as each of the emitter arrays and configuredto capture light emitted from emitter arrays 802 a-d. An aperture layerof a receiver channel array for sensor array 806 can define fourdistinct, non-overlapping fields of view for each photosensor 808, whereeach distinct field of view is aligned with a corresponding field ofview of one emitter from each emitter array 802 a-d. For instance,photosensor 810 can have four distinct fields of view that are definedby the aperture layer, where each aperture (shown as circles) is alignedto have the same field-of-view as one of: emitter 812 in emitter array802 a, emitter 814 in emitter array 802 b, emitter 816 in emitter array802 c, and emitter 818 in emitter array 802 d. Thus, when emitters 812,814, 816, and 818 are synchronized to emit light at their respectivetimes to illuminate their respective locations (e.g., pixels) in thefield, photosensor 810 will capture the emitted light through therespective aperture after they have been reflected off of objects in thefield. This concept can be appreciated with reference to the zoomed-inperspective 801 of photosensor 810 with fields of view of respectiveemitters 812, 814, 816, and 818 (shown as circles) superimposed overregions of the field of view of photosensor 810 (shown as a square). Asillustrated, the field of view of each emitter 812, 814, 816, and 818overlaps with a portion of the field of view of photosensor 810 so thatphotosensor 810 can capture their emitted light after being reflectedoff of objects in the field. In some embodiments, emitter arrays 802a-802 d emit light individually and in sequential order. For instance,emitter array 802 a can perform one emission cycle first (e.g., per bankfrom left to right), and then emitter array 802 b can perform oneemission cycle next, and so on and so forth until emitter array 802 dhas performed one emission cycle. Once every emitter array has completedone emission cycle, the sequential order can repeat again to captureanother image of the field.

As can be appreciated in FIG. 8A, by using multiple emitter arrays 802a-d, the total number of emitters for capturing a high resolution imageby sensor array 806 can be divided by the number of emitter arrays,which is four in this case, thereby resulting in emitter arrays withfewer emitters that are spaced farther apart. As a result, the powerload necessary for illuminating the field for capturing the highresolution image with sensor array 806 can be divided amongst emitterarrays 802 a-d (e.g., divided by four). Accordingly, drivers 804 a-d foreach emitter array only need to provide one fourth of the power (i.e.current) when compared to systems that only have one emitter array,while still being able to capture a high resolution image of the scene.Alternatively, since the number of light emitters per driver is reduced,each driver can provide more current to the light emitters, therebycausing the emitters to output more light and thus improving the imagecapture capabilities of LIDAR system 800. During operation, each emitterarray 802 a-d can perform one emission cycle, as discussed herein withrespect to FIGS. 6-7B, and in sequential order, such that one full scanof the scene is performed once all of the emitter arrays have performedan emission cycle.

In some embodiments, each emitter array 802 a-d and sensor array 806 arepositioned behind their own respective bulk imaging optic. When arrangedin conjunction with the bulk imaging optic, each emitter array 802 a-dcan form a light emission system and sensor array 806 can form a lightsensing system. In certain embodiments, the light emission systems canbe arranged symmetrically around the light sensing system, and can bepositioned as close to the light sensing system as possible to minimizeparallax. For instance, as shown in FIG. 8A, light emitter systems(represented by emitter arrays 802 a-d) can be symmetrically arrangedabove, below, and on both sides of the light sensing system (representedby sensor array 806).

Although FIG. 8A only shows four light emission systems organized in asymmetrical arrangement, embodiments are not limited to suchconfigurations and that other embodiments can have more or less lightemission systems and in asymmetrical arrangements. For instance, somesolid state electronic scanning LIDAR systems can have three lightemission systems positioned above or below and on both sides of thelight sensing system, or two light emission systems that are positionedabove or below and on the left or right side of the light sensingsystem. In embodiments where there are only two light emission systems,a single sensor array can be configured to capture light from twoemitter arrays. Accordingly, each emitter array can have an emitterarray density that is one half that of an emitter array for LIDARsystems with only one light emission system. In such embodiments, eachphotosensor in the sensor array can correspond to only two lightemitters, one from each emitter array.

In some embodiments, an aperture layer and a micro-lens array can beimplemented in front of the photosensor to enable the overlapping fieldsof view between a photosensor and a plurality of light emitters. Eachaperture can be aligned with a respective micro-lens and both theaperture and aligned micro-lens can correspond to a respective lightemitter of the plurality of light emitters. As an example, FIG. 8B is asimplified illustration of a micro-lens array 820 superimposed over anindividual photosensor 810, according to some embodiments of the presentdisclosure. Because the individual photosensor 810 is shared betweenfour different fields of view in a time multiplexed manner, thisapproach may allow for more per pixel processing logic to be fit intoeach photosensor because the pitch between photosensors is four timesgreater than the pitch between emitter and detector fields of view. Inthis embodiment it may be practical to embed a TDC, SRAM, and DSPdirectly in each photosensor 810 to enable each photosensor to be readout individually. The field of view of each micro-lens in micro-lensarray 820 can be defined by a corresponding aperture in the aperturelayer. In this example, micro-lens array 820 includes four micro-lenses822, 824, 826, and 828 aligned with their associated apertures, each ofwhich can correspond with, and be aligned to have the same field-of-viewas, a respective light emitter from each emitter array 802 a-802 d. Forinstance, micro-lens 822 can correspond with, and be aligned to have thesame field-of-view as, emitter 812, and the same can be said formicro-lens 824 and emitter 812, micro-lens 826 and emitter 816, andmicro-lens 828 and emitter 818. The pitch of micro-lens array 820 can befiner than the pitch of sensor array 808 so that micro-lens array 820can fit over a single photosensor. For instance, as shown in FIG. 8B,the pitch of micro-lens array 820 can be half the pitch of photosensorarray 808. Accordingly, the micro-lens array enables the sensor array tocapture a greater number of fields of view (i.e., capture an image witha higher resolution) than a sensor array without such a micro-lensarray.

FIG. 8C is a simplified cross-sectional view of micro-lens array 820positioned in front of photosensor 810 when sensing light from thefield, according to some embodiments of the present disclosure. In someembodiments, micro-lens array 820 can be positioned between bulk imagingoptics 830 and photosensor 810 such that light received from the fieldfirst passes through micro-lens array 820 before exposing on photosensor810. As shown in FIG. 8C, light 836 can be reflected light that wasemitted from emitter 816, and light 838 can be reflected light that wasemitted from emitter 818 at another instance of time. Light 836 can passthrough bulk optics 830 and expose on micro-lens 826 after it hasfocused to a point at an aperture layer 834 positioned along a focalplane of bulk imaging optics 830 for defining the discrete field ofviews for photosensor 810 and reducing stray light, as discussed abovewith respect to FIG. 5. Once light 836 passes through an aperture inaperture layer 834 and micro-lens 826, light 836 can collimate and passthrough a secondary optic 832, which can be configured to divert andrefocus light 836 onto photosensor 810. In some embodiments, micro-lensarray 820 and secondary optic 832 are implemented within the receiverchannel for photosensor 810 such that micro-lenses 822, 824, 826, and828 are all positioned within sidewalls 840 that form a tunnel aroundthe path of light to mitigate crosstalk between photosensors. Secondaryoptic 832 can focus light passing through each micro-lens 822, 824, 826,and 828 onto photosensor 810. In some embodiments, photosensor 810 isformed of a plurality of SPADS, where a subset of the plurality of SPADSis positioned to receive light from a corresponding micro-lens 822, 824,826, and 828. In alternative embodiments, the entire plurality of SPADSis positioned to receive light from each micro-lens 822, 824, 826, and828, such that the entire plurality of SPADS is readout four times, oncefor detecting light through each micro-lens 822, 824, 826, and 828 attheir respective times.

To further mitigate crosstalk, MEMS devices can be implemented over theaperture layer and along the light propagation path for each micro-lensto prevent crosstalk between micro-lenses. For instance, an array ofMEMS shutters (not shown) can be implemented between aperture 834 andbulk imaging optics 830 where each shutter is positioned over arespective aperture. The array of MEMS shutters can be operated toenable light to pass through the MEMS shutter when the correspondingemitter is emitting light, and prevent light to pass through when thecorresponding emitter is not emitting light. By implementing such a MEMSshutter array, the signal-to-noise ratio for photosensor 810 can beimproved.

Instead of having non-overlapping field of views for each emitter arrayand increasing the resolution of the detector array as discussed abovewith respect to FIGS. 8A-8C, in some embodiments of the disclosure thefield of view for the emitter arrays can overlap one another therebyproviding increased brightness and redundancy for each position in thefield of view. That way, if one emitter from one emitter array fails, oreven if an entire emitter array fails (e.g., due to damage from flyingdebris) the solid state electronic scanning LIDAR system can stillproject emitted light into the field of view of the photosensorassociated with the damaged emitter with the additional one or moreemitters that are aligned to that field-of-view. Thus, the resultingsystem can be more robust and reliable. An example of this embodiment isshown in FIG. 8D.

FIG. 8D is a simplified illustration of an exemplary LIDAR system 850including a plurality of independently operable emitter arrays 852 a-bhaving overlapping fields of view, each with their own set of drivers854 a-b, for emitting light that can be captured by a sensor array 856,according to some embodiments of the present disclosure. Emitter arrays852 a, 852 b and their respective drivers 854 a, 854 b can be arrangedaccording to banks as discussed above with respect to FIGS. 6 and 7A orcan be arranged in independently addressable columns as discussed withrespect to FIG. 7B or can be arranged into any arbitrary subset of drivecircuits across the array. Each emitter array 852 a, 852 b can includean m×n (same sized) array of emitters as described in variousembodiments above with the arrays being directed to the same field ofview in the far field. For example, as shown in FIG. 8D, the column 1,row 1 of emitter array 852 a is emitter 862, and the column 1, row 1 ofemitter array 852 b is emitter 864. Each emitter 862 and 864 can bealigned to project into the same distinct discrete field-of-view beyonda threshold distance.

Sensor array 856 can include an array of photosensors 858 arranged inthe same m×n configuration as each emitter array 852 a, 852 b and can beconfigured to capture light emitted from emitter arrays 852 a, 852 b.Specifically, each photosensor can have a one-to-one correspondence witha respective emitter in each emitter array 852 a, 852 b. For instance,photosensor 860 can be associated with, and aligned to have the samefield of view as, emitter 862 in emitter array 852 a and emitter 864 inemitter array 852 b. Thus, when emitters 862 and 864 are fired to emitlight to illuminate the same location (e.g., discrete spot) in thefield, photosensor 860 will capture the emitted light from each ofemitters 862 and 864 after the light has been reflected off of objectsin the field. This concept can be appreciated with reference to FIG. 8Eas well as the zoomed-in perspective 851 of photosensor 860 shown inFIG. 8D.

Referring first to FIG. 8D, the overlapping fields of view of respectiveemitters 862 and 864 are shown as a single circle superimposed over thefield of view of photosensor 860 (shown as a square). As illustrated,the field of views of emitters 862 and 864 overlap with a same portionof the field of view of photosensor 860 so that photosensor 860 cancapture light from each of emitters 862, 864 after the light isreflected off of one or more objects in the field.

FIG. 8E further illustrates this concept. FIG. 8E is a simplifiedillustration of the field of view for an individual receiver channel insensor array 856 and the overlapping fields of view for correspondingemitters in emitter arrays 852 a, 852 b. Each emitter in emitter arrays852 a, 852 b can emit a pulse of light shown in FIG. 8E as cones 870 aand 870 b that gets collimated through separate bulk transmitter optics872 a, 872 b. The collimated light from each emitter array is thenoutput to the field as pulses of discrete beams 874 a, 874 b.

As shown in FIG. 8E, emitter arrays 852 a, 852 b are co-aligned suchthat each of the discrete beams 874 a, 874 b have identical fields ofview 880 beyond a threshold distance. In this manner the amount of lightfocused at the discrete spot represented by field-of-view 880 can beincreased as compared to a single beam and the multiple beams of lightprovide redundant illumination at each photosensor field of view. Eachemitted beam of light 874 a, 874 b can reflect off of one or moreobjects in the field and propagate back towards sensor array 856 asreflected light 882. The reflected light 882 then propagates throughbulk receiver optic 884, which focuses the reflected light into a focalpoint as a cone of pulsed light 886 and then onto a correspondingphotosensor (e.g., photosensor 860) within sensor array 856. Sinceemitters 862 and 864 project light into the same field of view, if oneof emitters 862 or 864 fails to operate, photosensor 860 can stillcapture light at the particular location (e.g., discrete spot) in thefield emitted from the other emitter providing a beneficial level ofredundancy. Additionally, when both emitters are operating to emit lightfor a single photosensor, the photosensor has improved sensingperformance.

As can be understood with reference to FIG. 8E, the distance betweenadjacent bulk transmitter optics 872 a, 872 b and bulk receiver optic884, which as an example can range between 0.5 to 5 cm, is relativelysmall compared with the distance to the scene. Thus, as the scene getsfarther, the field of view for each emitter array 852 a, 852 bincreasingly overlaps with each other and with the field of view forsensor array 856. For instance, as shown in FIG. 8E, overlapping regions890, 892, and 894 of the fields of view for the emitter arrays andsensor array get larger as the distance to the scene increases. Thus, atdistances near the end of the scene, e.g., objects in the field, thefield of view of emitter array 852 a can substantially overlap the fieldof view of sensor array 856 and the field of view of emitter array 852 bcan also substantially overlap the field of view of sensor array 856.Accordingly, each corresponding emitter pair and sensor can observeessentially the same point in the scene even though the bulk receiverand transmitter optics are separated by one or more centimeters. Thatis, each illuminating beam projected from bulk transmitter optic 872 a,872 b into the field external to the system can be substantially thesame size and geometry as the field of view of a correspondingphotosensor (or a micro-optic receiver channel for the correspondingphotosensor) at a distance from the system.

Although FIGS. 8D and 8E illustrate an embodiment in which two emitterarrays 852 a, 852 b provide both increased brightness and redundancy inLIDAR system 850, embodiments of the disclosure are not limited to suchconfigurations. Other embodiments can have more than two emitter arraysfor greater reliability. For instance, some embodiments can have three,four, or more emitter arrays that have overlapping fields of view. Thatway, if one, two, or more emitter arrays fail and one emitter array isstill operable, the LIDAR system can still operate to capture an imageof the field. Additionally, instead of only having more emitter arrays,other embodiments can have more than one sensor array that haveoverlapping fields of view. These multiple sensor arrays may besynchronized temporally and their data combined in a downstreamcontroller to improve sensor performance or redundancy. In suchembodiments, the same concept from multiple emitters can be applied toinstances where there are multiple sensor arrays (and thus multiplereceivers).

3. MEMS Devices for Light Emission Systems

Embodiments above discuss two-dimensional emitter arrays for projectinga two-dimensional light pattern within a field. Some embodiments of thedisclosure, however, can instead include a transmitting element formedof a one-dimensional array of light emitters or just a single lightemitter. In such embodiments, one or more microelectromechanical systems(MEMS) devices can be modulated to reflect the light of aone-dimensional array of light emitters into a two-dimensional lightpattern within a field, as discussed herein with respect to FIGS. 9A and9B.

FIG. 9A is a simplified illustration of an exemplary light emissionsystem 900 that includes a one-dimensional emitter array 902 and a MEMSdevice 904, according to some embodiments of the present disclosure. Itis to be appreciated that FIG. 9A is not drawn to scale and thus emitterarray 902 may not necessarily be larger than MEMS device 904 in anactual implementation. MEMS device 904 can be any suitable MEMS devicethat can reflect received light in any predetermined pattern. Forinstance, MEMS device 904 can be a tilt mirror that can tilt/scan in oneor more dimensions. As shown in FIG. 9A, MEMS device 904 can tilt/scanin a single, horizontal direction (i.e., scanning axis 918) to produce alight pattern 916 within the field. In such embodiments, emitter array902 is oriented perpendicular to the scanning axis 918. The resultinglight pattern 916 can be a two-dimensional pattern that is projectedupon a scene and reflects back to a sensor array that is configured todetect the two-dimensional pattern of reflected light. Thus, the fieldof view of emitter array 902 can match the field of view of thecorresponding sensor array, as discussed herein with respect to FIG. 4,even though there is no one-to-one correlation between emitter array 912and the sensor array.

In some embodiments, emitter array 902 and MEMS device 904 can producelight pattern 916 under the control of controller circuitry, e.g.,ranging system controller 104 in FIG. 1, to which emitter array 902 andMEMS device 904 are coupled. The controller circuitry can be configuredto execute a plurality of image capture periods (i.e., one emissioncycle) where, for each image capture period, emitter array 902 issequentially fired while MEMS device 904 is tilted along its scanningaxis until the two-dimensional illumination pattern, i.e., light pattern916, is generated. In some instances, emitter array 902 is formed of nnumber of light emitters that is repeatedly emitted m number of imagecapture periods while MEMS device 904 is continuously tilting along thescanning axis. Thus, the resulting illumination pattern is an m×n arrayof discrete beams of light.

FIG. 9B is a simplified illustration of an exemplary light emissionsystem 901 that includes a single emitter 912 and a MEMS device 914,according to some embodiments of the present disclosure. Instead of anarray of emitters, light emission system 901 can only include oneemitter 912 that emits light into a field. When configured as aone-dimensional tilt mirror, MEMS device 904 can only project emittedlight into a single dimension, not two dimensions to match a sensorarray. Thus, MEMS device 904 can be paired with an optical element thatcan diffract the received light into a second dimension. As an example,MEMS device 904 can be paired with a diffractive optical element 926that is positioned to receive light after it has reflected off of MEMSdevice 904. Diffractive optical element 926 can be configured todiffract received light in a dimension along which MEMS device 904 doesnot tilt. As an example, if MEMS device 904 tilts along the x-direction,diffractive optical element 926 can diffract received light in they-direction. Thus, when paired with MEMS device 904, the resulting lightpattern can be a two-dimensional pattern of light emissions (i.e.,discrete beams of light).

During operation, emitter 912 and MEMS device 904 can produce lightpattern 916 under the control of controller circuitry, e.g., rangingsystem controller 104 in FIG. 1, to which emitter array 902 and MEMSdevice 904 are coupled. The controller circuitry can be configured toexecute a plurality of image capture periods where, for each imagecapture period, emitter 912 is sequentially fired while MEMS device 904is tilted along its scanning axis. Diffractive optical element 926 canbe positioned downstream from MEMS device 904 such that light reflectedby MEMS device 904 passes through diffractive optical element 926 and isdiffracted into n number of discrete beams of light. The n number ofdiscrete beams of light can be repeatedly generated while MEMS device904 is tilted until the two-dimensional illumination pattern, i.e.,light pattern 916, is generated. In some instances, emitter 912 isrepeatedly emitted m number of image capture periods so that theresulting illumination pattern is an m×n array of discrete beams oflight.

In some embodiments, MEMS device 904 can be a tilt mirror that cantilt/scan in two dimensions to achieve a resulting emitted light patternthat is in two-dimensions. That is, MEMS device 904 can tilt/scan inboth the horizontal and vertical directions (i.e., scanning axes 920 and922) to produce a light pattern 924 within the field, therebyeliminating the need for a separate diffractive element, e.g.,diffractive optical element 926. Like pattern 916, light pattern 924 canbe a two-dimensional pattern that is projected upon a scene and reflectsback to a sensor array that is configured to detect the two-dimensionalpattern of reflected light. Thus, the field of view of emitter array 912can match the field of view of the corresponding sensor array, asdiscussed herein with respect to FIG. 4, even though there is noone-to-one correlation between emitter array 912 and the sensor array.

Although not shown, it is to be appreciated that the light emittersdiscussed in FIGS. 9A-9B can be paired with one or more correspondingmicro-lenses that collimates the light and directs it substantially ontothe MEMS devices. Additionally, other diffractive elements or opticalelements can be used to directed the emitted light toward MEMS device904.

4. Enhanced Light Emission System

Embodiments of the present disclosure pertain to a LIDAR sensor thatcan, among other uses, be used for obstacle detection and avoidance inautonomous vehicles. Some specific embodiments pertain to LIDAR sensorsthat include design features that enable the sensors to be manufacturedcheaply enough and with sufficient reliability and to have a smallenough footprint to be adopted for use in mass-market automobiles,trucks and other vehicles. For example, some embodiments include a setof vertical-cavity surface-emitting lasers (VCSELs) as illuminationsources that emit radiation into a field and include arrays ofsingle-photon avalanche diode (SPAD) detectors as a set of photosensors(detectors) that detect radiation reflected back from a surface in thefield. Using VCSELs as the emitters and SPADs as the detectors enablesmultiple measurements to be taken at the same time (i.e., the VCSELemitters can be fired simultaneously) and also enables the set ofemitters and the set of photosensors to each be fabricated usingstandard CMOS processes on a single chip, greatly simplifying themanufacturing and assembly process.

Using VCSELs and SPADs in certain embodiments presents challenges,however, that various embodiments of the present disclosure overcome.For example, VCSELs are much less powerful than typical lasers used inexisting LIDAR architectures and SPADs are much less efficient than thetypical detectors used in the existing LIDAR architectures. To addressthese challenges, as well as challenges presented by firing multipleemitters simultaneously, certain embodiments of the disclosure includevarious optical components (e.g., lenses, filters, and an aperturelayer), which may work in concert with multiple arrays of SPADs, eacharray corresponding to a different pixel (e.g., position in the field),as described herein. For example, as discussed herein with respect toFIG. 1, optical system 128 of light sensing module 108 can include amicro-optic receiver layer (not shown in FIG. 1) for enhancing the lightdetected by sensor array 126, which can include an array ofphotosensors, each of which can be an array of SPADs.

Because VCSELs are less powerful than typical lasers in existing LIDARarchitectures, in some embodiments, a light emission system can beconfigured to improve the ability of an solid state electronic scanningLIDAR system to perform light ranging functionality. That is, thequality of light emitted by the light emission system can be enhanced toimprove light ranging accuracy and efficiency. The quality oftransmitted light for light ranging and imaging purposes can be definedin terms of brightness and intensity. The brightness and intensity oflight rays emitted from bulk transmitter optic can be enhanced bymodifying and/or implementing one or more optic transmitter layers, aswill be discussed further herein.

Brightness of a transmitting light can be defined by the optical power(in watts) per solid angle. Thus, light sources that output light withtight collimation, i.e., low divergence, produce light that are high inbrightness. Conversely, light sources that output light with highdivergence produce light that are low in brightness. Intensity of lightcan be defined by the optical power per area, meaning light emitted witha certain power will have higher intensity if it tightly compacted in asmall area. Accordingly, light sources that output light in a tightlycompacted ray will have higher intensity than light sources that outputlight in a less compacted ray, even if both light sources output lightthat has low divergence. As will be appreciated herein, transmittercomponents for LIDAR systems in embodiments of the present disclosurecan be configured with micro-optical components that enable thetransmitter to output light that has enhanced brightness and intensityas compared to a similar transmitter without the micro-opticalcomponents.

FIG. 10 is a simplified cross-sectional view diagram of an exemplaryenhanced light emission system 1000, according to some embodiments ofthe present disclosure. Light emission system 1000 can include a lightemitter array 1002 having light emitters 1004 that for example maycomprise without limitation any of LEDs, laser diodes, VCSELs, or thelike for emitting light 1013. A VCSEL is a type of semiconductor laserdiode with laser beam emission perpendicular from the top surface. Notethat the linear array shown in FIG. 10 can be any geometric form ofemitter array, including and without limitation circular, rectangular,linear, or any other geometric shape.

Enhanced light emission system 1000 can include a micro-optictransmitter channel array 1006 separated from light emitter array 1002by an open space 1018. Each micro-optic transmitter channel 1008 can bepaired with a corresponding receiver channel (e.g., receiver channel 512in FIG. 5) and the centers of their fields-of-view are aligned to beoverlapping at a certain distance from the optical imager system.Micro-optic transmitter channel array 1006 can be formed of a substrate1019 sandwiched between a first optical surface 1020 positioned on aside facing light emitter array 1002 and a second optical surface 1021positioned on an opposite side facing away from light emitter array1002. Both first and second optical surfaces 1020 and 1021 can each beconfigured as an array of convex, micro-optic lenses where each convexlens of first optical surface 1020 is configured to be optically alignedwith a respective convex lenses of second optical surface 1020 so thatlight transmitting through first optical surface 1020 can subsequentlybe transmitted through second optical surface 1021. The correspondingconvex lenses from first and second optical surfaces 1020 and 1021 canface away from one another as shown in FIG. 10. In certain embodiments,convex lenses of first optical surface 1020 have a first optical powerand convex lenses of second optical surface 1021 have a second opticalpower different from the first optical power. For instance, the secondoptical power can be greater than the first optical power such that thefocal length of the second optical power is shorter than the focallength of the first optical power. Substrate 1019 can be formed of anysuitable material that is transmissive in the wavelength range of thelight emitters 1004 such silicon, silicon dioxide, borosilicate glass,polymer, and the like. First and second optical surfaces 1020 and 1021can be formed of a transparent polymer that is imprinted on respectiveopposite surfaces of substrate 1019.

In some embodiments, micro-optic transmitter channel array 1006 can beformed of a monolithic array of micro-optic transmitter channels 1008.Each micro-optic transmitter channel 1008 can include a first convexlens from first optical surface 1020, a corresponding second convex lensfrom second optical surface 1021, and a corresponding portion ofsubstrate 1019 positioned between the two convex lenses. Eachmicro-optic transmitter channel 1008 can correspond with a respectivelight emitter 1004 so that light outputted from the light emitter 1004first passes through the first convex lens, through the correspondingregion of substrate 1019, and then through the second convex lens duringoperation.

Once light emits out of the second convex lens of second optical surface1021, the light forms a miniature spot image 1010 that is a real imageof the corresponding light emitter 1004 but a reduced-size of thecorresponding light emitter 1004. In some embodiments, miniature spotimages 1010 are positioned between micro-optic transmitter channel array1006 and bulk transmitter optic 1014. For instance, miniature spotimages 1010 can be formed within respective apertures of an aperturelayer 1009. Each aperture can be a pin hole in a reflective or opaquelayer in which emitted light focuses to form miniature spot images 1010.It is to be appreciated that aperture layer 1009 is optional and lightenhancing capabilities of micro-optic transmitter channel array 1006 canbe achieved without aperture layer 1009. In such embodiments, miniaturespot images 1010 can be formed at a focal plane of the second convexlens of second optical surface 1021. From there, continuing away fromboth the light emitter and micro optic channel, the light forms a lightcone 1012 reaching out towards bulk transmitter optic 1014.

According to some embodiments of the present disclosure, the degree ofdivergence of emitted light 1013 can be smaller than the degree ofdivergence of light cone 1012. This discrepancy in divergence can becreated by a micro-optic transmitter channel 1008, specifically by theoptical power of second optical surface 1021. Because the divergence oflight out of micro-optic transmitter channel 1008 is larger than thedivergence of emitted light 1013 from light emitters 1004, miniaturespot image 1010 can be a real image of light emitter 1004 but amultitude smaller than the size of light emitter 1004 and with the samenumber of photons as emitted light 1013. The resulting light cone 1012formed after the real spot images are formed then gets projected intothe field as discrete beams of light for each light emitter 1004 afterpassing through bulk transmitter optic 1014. The resulting light raysemanating out of light emission system 1000 are highly collimated beamsof light that have a small cross-sectional area, thereby resulting in alight emission system 1000 that can output light having enhancedbrightness and intensity. In contrast, a system with no micro-opticchannel array that instead has light emitter array 1002 at the focalplane of bulk transmitter optic 1014 would produce beams that aresignificantly less collimated, and these beams would therefore have alarger cross-sectional area in the far field.

Note that bulk transmitter optic 1014 can include either a single lensor a cluster of lenses where two or more lenses function together toform bulk transmitter optic 1014. The use of multiple lenses within thebulk transmitter optic 1014 could increase the numerical aperture,reduce the RMS spot size, flatten the image plane, improve thetelecentricity, or otherwise improve the performance of bulk transmitteroptic 1014. Note also that for some embodiments, light cones 1012 mayoverlap forming cone overlap region 1016.

To better understand the operation and effectiveness of micro-optictransmitter channel array 1006, a more detailed explanation of theoperation of light emission system 1000 is discussed. For enhanced lightemission systems 1000 utilizing a light emitter array formed of VCSELemitters, an exemplary initial radius for an emitter might be 12.5 umwith light admitted in a 10° half angle cone. Such emitters wouldtypically output 50 uW per square micron of active area. A diverginglight cone from each emitter 1004 is accepted into a micro-optictransmitter channel 1008, and then a converging light cone is output bythat same micro optic channel to produce a converging light cone with ahalf angle of for example 20°. Thus for some embodiments, the cone angleproduced by an emitter 1004 is smaller than the cone angle produced by acorresponding micro-optic transmitter channel 1008. The converging lightcone emanated by micro-optic transmitter channel 1008 then produces aminiature spot image 1010 of the emitter. For the embodiment accordingto FIG. 10, miniature spot image 1010 is a real image and has a sizethat is smaller than the size of a corresponding light emitter 1004.Note that all rays from a given emitter may not all be focused into anarbitrarily small spot. The miniature spot image size is typicallycontrolled by an “optical invariant”:

Θ_s*r_s>=Θ_e*r_e

where Θ_s is the marginal ray half angle of the focused spot, r_s is theradius of the focused spot, Θ_e is the marginal ray half angle of theoriginal emitter, and r_e is the radius of the original emitter. So, inthis example, the smallest miniature spot image radius that could beformed (while still capturing all the rays from the emitter) is:

10/20*12.5 um=6.25 um

Note that this smaller spot will have one fourth the area of theoriginal emitter, and thus has a power density of 200 uW per squaremicron of spot area. Each micro-optic transmitter channel 1008 typicallyhas one or more optical surfaces, having characteristics that may forexample and without limitation include a focal length of 50 um, and alens diameter of 80 um. For some embodiments, the distance between lightemitter 1004 and a corresponding micro-optic transmitter channel 1008may be for example and without limitation 150 um. Open space 1018between emitter array 1002 and micro-optic transmitter channel array1006 as shown in FIG. 10 may be, for example and without limitation anair gap such as that produced by methods typically used to manufactureMEMS devices. The distance between emitter array 1002 and micro-optictransmitter channel array 1006 for example may be 150 um.

Bulk transmitter optic 1014 is positioned in front of the micro-opticand emitting layers such that the focal plane of the bulk imaging opticcoincides with miniaturized spot images 1010. Bulk transmitter optic1014 accepts divergent light cone(s) 1012 and outputs a collimated beam.Its numeric aperture can be at least large enough to capture the fullrange of angles in the divergent ray cone(s), so for example and withoutlimitation the Numerical Aperture (NA)=0.34 in this example. Also, bulktransmitter optic 1014 can be image-space telecentric, since lightcone(s) 1012 exiting the micro-optic layer may all be parallel (ratherthan having their center axes aimed towards the center of the bulkoptic). In one embodiment, light can exit bulk transmitter optic 1014approximately collimated. Note that the quality of beam collimationrelates to the size of the “emitting object” (miniature spot images1010) at the focal plane. Since this “emitting object” size has beenreduced by using a micro-optic stack, a better collimation angle isobtained than if the emitter object was simply imaged directly.

Although FIG. 10 shows an enhanced light emission system having amicro-optic channel array formed of a substrate sandwiched between firstand second optical surfaces, and positioned a distance away from a lightemitter array by an open space to improve the brightness and intensityof light outputted by the light emission system, embodiments are notlimited to such configurations. Rather, other embodiments may notnecessarily implement an open space or two optical surfaces, asdiscussed in further detail in related U.S. patent application Ser. No.15/979,235, entitled “Optical Imaging Transmitter with BrightnessEnhancement”, filed on May 14, 2018, and incorporated herein byreference in its entirety for all purposes.

III. Configuration and Operation of Sensor Arrays

Once light is reflected back to the electronic scanning LIDAR system,the light detection system receives the light by first having the lightpass through the bulk receiving optics, which focuses down the lightthrough an aperture layer and exposes the light onto a plurality ofphotosensors in a sensor array. In some instances, the light canpropagate through an optical filter before passing through the aperturelayer. When light exposes onto the sensor array, each photosensor isdetecting a discrete amount of light that, when analyzed in conjunctionwith all of the photosensors in the sensor array, can be used togenerate an image of a scene within a field. That is, each photosensorcan be read by external circuitry to build the image of the scene.According to some embodiments, the sensor array can be operated invarious ways, as will be discussed herein with respect to FIGS. 11-13.

FIG. 11 is a simplified diagram of a sensor array control system 1100for operating an m×n sensor array 1102 per column, according to someembodiments of the present disclosure. Sensor array control system 1100can include column selecting circuitry 1104, one or more time-to-digitalarrays 1106, and one or more static random access memory (SRAM) deviceson a digital signal processor (DSP) array 1108. Column selectingcircuitry 1104 can be any suitable circuitry configured to select whichcolumn to read and in what specific sequence. In some embodiments,column selecting circuitry 1104 can be configured to operate insynchronization with the drivers in the light emission system so thatthe selected column in sensor array 1102 can correspond to the activatedcolumn in the emitter array, as discussed herein with respect to FIGS. 2and 3. TDC array 1106 can be configured to translate the signalgenerated by photons detected at the photosensors into a digital timeseries of the events. The time series can be a sequence of photon countsthat represent the reflected photon flux back to the photosensor versustime, which can be used to determine the shapes and distance of objectsaround the scene. The SRAM and DSP array 1108 can be any suitablemicrocontroller or processor configured to process the received signalsfrom the photosensors in sensor array 1102.

In some embodiments where the sensor array is formed on a single ASIC,the time-to-digital arrays 1106 and DSP 1108 can be pushed to the edgesof the ASIC and positioned around sensor array 1102. Such a designleaves a lot of space for the light sensitive pixels (e.g., arrays ofSPADs) in the active region of the receiver ASIC thereby enabling thecollection of more light and improved performance.

During operation, column selecting circuitry 1104 can select one or morecolumns to read, and that selected column can be read by operation ofTDC array 1106 and SRAM/DSP array 1108. For instance, column selectingcircuitry 1104 can select column 1110 which can then be read byoperating TDC array 1106 and SRAM/DSP array 1108. As shown in FIG. 11,the photosensors for each column can be read out by reading every row insensor array 1102. In some embodiments, instead of reading only one rowat a time, multiple rows can be read at one time. For example, sensorcontrol system 1100 can include two TDC arrays 1106 and two SRAM/DSParrays 1108, one on each side of sensor array 1102. Thus, duringoperation, column selecting circuitry 1104 can select two columns, e.g.,1110 and 1112, to read, in which case, the respective TDC array 1106 andSRAM/DSP array 1108 can read the columns, e.g., column 1110 can be readout by the arrays 1106 and 1108 to the left while column 1112 can beread out by the arrays 1106 and 1108 to the right. Such a design allowsthe simultaneous firing of two columns of emitters that correspond tothe two columns of photosensors that are readout concurrently. The timeseries of the pulse trains as detected by each photosensor can be storedin the SRAM memory bank in SRAM/DSP array 1108 so that the SRAM memorycan provide this information to the DSP or any other processor, e.g.,processor 122 or 130 in FIG. 1. In some embodiments, the SRAM capacitycan be doubled such that there are two identical banks instead of onefor reading sensor array 1102. Accordingly, when one bank reads in thedata from one pixel column, the other bank can push out the data to adigital signal processing system. This architecture allows for twice thedata pipelining, and twice the pixel capture rate of a system with asingle SRAM bank.

In addition to being read out by column, some embodiments can beconfigured so that a sensor array is read out by row, as discussedherein with respect to FIG. 12. FIG. 12 is a simplified diagram of asensor control system 1200 for operating an m×n sensor array 1202 perrow, according to some embodiments of the present disclosure. Sensorcontrol system 1200 can include row selecting circuitry 1204 and TDCarrays and SRAM/DSP arrays, which is shown as a single combined modulelabeled TDC and SRAM/DSP array 1206. Row selecting circuitry 1204 canhave substantially the same configuration and operation as columnselecting circuitry 1104 in FIG. 11, but that it operates to selectphotosensors by row instead of column. TDC and SRAM/DSP array 1206 canhave substantially the same configuration and operation as both TDCarray 1106 and SRAM/DSP array 1108 in FIG. 11, but that it operates toread the photosensors by row instead of column. Thus, row selectingcircuitry 1204 can select the row to read and TDC and SRAM/DSP array1206 can perform the read operation.

Although FIGS. 11 and 12 illustrate embodiments where an entire row orcolumn is read at a time, embodiments are not so limited. Instead, otherembodiments can be configured to individually select one or morephotosensors in the sensor array. FIG. 13A is a simplified diagram of acontrol system 1300 for operating an m×n sensor array 1302 perphotosensor with column and row control circuits, according to someembodiments of the present disclosure. Instead of having only one columnor row selecting circuitry and only one corresponding TDC and SRAM/DSParray, sensor control system 1300 can include both column selectingcircuitry 1304 as well as row selecting circuitry 1306, and TDC andSRAM/DSP arrays 1308 and 1310 for reading out by row and column. Thatway, sensor control system 1300 can select specific one-dimensionalgroups of photosensors by selecting the specific row and column in whichthe desired photosensor lies. As an example, sensor control system 1300can select only photosensor 1312, and/or groups of one-dimensionalphotosensors 1314 and 1316. Once those photosensors are selected, thenthey can be read out by the respective column and/or row TDC andSRAM/DSP arrays 1308 and 1310.

In some additional embodiments, instead of reading out the photosensorsinto column or row end TDCs and memory (SRAM), the photosensors can beread out into per pixel TDC's and memory so that any configuration ofphotosensors of one- or two-dimensions can be enabled at once. As anexample, FIG. 13B is a simplified diagram of a control system 1301 foroperating an m×n sensor array 1302 per photosensor with control circuitsspecific to each photosensor, according to some embodiments of thepresent disclosure. Here, instead of incorporating TDC and SRAM/DSParrays for columns and rows, separate TDC and SRAM devices can beimplemented adjacent to the photosensors or on an underlyingsemiconductor die for each respective photosensor to enable thesimultaneous readout of an arbitrary number and configuration ofphotosensor across the array. DSP arrays 1328 and 1330 can beimplemented off to the side of sensor array 1302 and be a sharedresource for the TDC and SRAM devices under each photosensor or the DSPcan also be incorporated into each pixel. In such embodiments, sensorarray 1302 can be fabricated as a stack of two or more monolithicelectronic devices (“semiconductor dies”) bonded together into a singlestructure with electrical signals passing between them. The topsemiconductor die can include sensor array 1302 that is fabricated by aprocess that maximizes photosensing efficiency or minimizes noise whilethe other dies for the TDC and SRAM devices are optimized for lowerpower, higher speed digital processing. With this configuration, sensorarray 1302 can be operated to select any one- or two-dimensional groupsof photosensors of any arrangement by selecting the specific row andcolumn in which the desired photosensors lie and having the respectiveTDC and SRAM device perform readout of the selected photosensorsindividually. As an example, sensor control system 1301 can selecttwo-dimensional groups of photosensors 1334 and 1336 in variousarrangements. Once those photosensors are selected, then they can beindividually read out by the respective TDC and SRAM device. Becauseselecting these two dimensional groups of photosensors may beaccomplished in under one microsecond and the groups are constantlycycled through, the sensor control system may contain configurationregisters that predefine a number of photosensor groups that correspondto the drive circuit groupings on a corresponding emitter array. Forinstance, in some embodiments there are 16 independent laser drive banksfor a laser emitter array and 16 separate configuration registers todefine the photosensor groupings and these configurations may beselected by a ranging system controller, or any other controllerdiscussed herein with respect to FIG. 1, that synchronizes the firing ofthe emitter array with the selection of its corresponding photosensorgroup. These grouping registers may be configured when the sensor arrayturns on and may be reprogrammed to change the sequencing of the groupsbased on control inputs from the ranging system controller or based oninformation from the target environment.

As discussed herein, an emitter array and a sensor array, and thus therespective micro-optic transmitter and receiver channels that manipulatelight for them, can correspond to one another such that light emittedfrom the emitter array can be detected by the sensor array. To helpillustrate the correspondence between the emitter and photosensors, anarray of apertures of the micro-optic transmitter channels can besuperimposed over an array of pixels of the micro-optic receiverchannels, as shown in FIGS. 14-16.

FIGS. 14-16 illustrate exemplary configurations for a sensor array withrespect to an emitter array where light emitters are represented bycircles (which, in some embodiments, can in turn be representative ofapertures of the micro-optic transmitter channels) and the photosensorsof the micro-optic receiver channels are represented by their owngeometric profile (i.e., squares/rectangles) for clarity purposes andease of understanding. It is to be appreciated that the emitter andsensor arrays shown in FIGS. 14-16 may only be representative of aportion of an actual emitter and sensor array, which can include manymore emitters and photosensors than shown in the figures. Furthermore,each photosensor shown in FIGS. 14-16 can be a single photodetector, ora plurality of SPADS.

FIG. 14 is a simplified illustration of a configuration 1400 where anemitter array and a sensor array have a one-to-one correspondence,according to some embodiments of the present disclosure. As shown, eachlight emitter 1402 can correspond with a respective photosensor 1404 sothat the light emitted by emitter 1402 can be detected by itscorresponding photosensor 1404 after the emitted light has reflected offof an object in the field. Horizontal and vertical sidewalls 1406 and1408 can mitigate cross talk between adjacent photosensors. In suchembodiments, the horizontal and vertical pixel pitch dimensions may bethe same. For instance, the horizontal and vertical pixel pitch of thesensor array for configuration 1400 can be 100 um×100 um.

In some embodiments, the dimensions of the photosensors can be alteredto modify the resolution of the sensor array in one or more directions.For instance, FIG. 15 is a simplified illustration of a configuration1500 where an emitter array and a sensor array have a one-to-onecorrespondence but at a modified resolution in one dimension, accordingto some embodiments of the present disclosure. As shown, eachphotosensor 1504 can have a larger length so that the verticalresolution is decreased when compared to the resolution of the sensorarray in configuration 1400 in FIG. 14. In such embodiments, eachphotosensor 1504 can be in the shape of a rectangle. By decreasing theresolution in one or more dimensions, more room is available in whichelectrical components can be mounted. In such embodiments, thehorizontal and vertical pixel pitch dimensions may be different. Forinstance, the horizontal and vertical pixel pitch of the sensor arrayfor configuration 1500 can be 100 um×200 um.

FIG. 16 is a simplified illustration of a configuration 1600 where asensor array has multiplexed photosensors, according to some embodimentsof the present disclosure. In a multiplexed photosensor arrangement,more than one photosensor can correspond to a single emitter in anemitter array, and some photosensors can correspond with more than oneemitter. For instance, the emitter array in configuration 1600 caninclude emitters 1602 a-h characterized by circles which represent thefield of view of the emitter as defined by the aperture for the emitter.Each emitter 1602 a-h can correspond with a plurality of photosensors1604 a-f in the sensor array. As an example, emitter 1602 a cancorrespond with four photosensors, photosensors 1604 a-d, that each haveat least some portion capable of capturing light emitted from emitter1602 a after it has reflected off of objects in the field. Although FIG.16 only shows an emitter corresponding with four photosensors, otherembodiments can have an emitter correspond with any other suitablenumber of photosensors, such as six, eight, or even sixteen. Having alarger number of photosensors for detecting light of a single emitterprovides more dynamic range for each pixel measured in the field, andallows a more densely packed sensor array to be implemented, which canimprove resolution.

In some embodiments, one or more photosensors can be configured to senselight from multiple emitters. As an example, the field of view ofemitter 1602 c can overlap with photosensors 1602 c-f; thus, since thefield of view of emitter 1602 a overlaps with photosensors 1602 a-d,photosensors 1602 c-d can correspond with both emitters 1602 a and 1602c. By enabling this sensing overlap, photosensor resources can beshared, thereby providing a more efficient sensor array. As can beappreciated in FIG. 16, to enable the operation of multiplexedphotosensors, sidewalls between photosensors in adjacent columns may notexist, and instead, only sidewalls 1606 between rows may exist. The lackof column walls in addition to the overlap of photosensors for differentemitters may suffer from cross-talk. Thus, it may be beneficial tomodulate the emitter array in a way that mitigates cross-talk betweenadjacent photosensors while still enabling the photosensor resources tobe shared. For instance, if the emitter array in FIG. 16 is a columnmodulated emitter array as discussed herein with respect to FIG. 2 whereemitters 1602 a-b are activated at once (likewise for emitters 1602 c-d,1602 e-f, and 1602 g-h), then the emitter array can be configured toactivate emitters 1602 a-b and 1602 e-f at a first instance in time, andthen emitters 1602 c-d and 1602 g-h at a second instance in time.Emitters 1602 a-b and 1602 e-f can be emitters from the same emitterarray or from different emitter arrays, which is discussed herein withrespect to FIGS. 8A and 8D.

Although FIG. 16 refers to each dotted square as an individualphotosensor, it is to be appreciated that embodiments are not limited tosuch implementations and that each dotted square can represent othersensing elements. For example, in some embodiments, each dotted squarecan represent an array of SPADS, or an individual SPAD. In this example,the array of dotted squares as a whole in configuration 1600 can operateas an amorphous sensing array that dynamically selects one or morearrays of SPADS or individual SPADS for readout depending on whichemitter 1602 a-h is emitting light. For instance, arrays of SPADS 1604a-d can be readout when emitter 1602 a is activated during a firstcapturing period, and arrays of SPADS 1604 c-f can be readout whenemitter 1602 a is activated during a second capturing period. Each arrayof SPADS 1604 a-d can correspond to a sub-region of a photosensor, assimilarly discussed herein with respect to FIG. 8C, or each array ofSPADS 1604 a-d can correspond to an individual photosensor.

IV. Solid State Construction of Electronic Scanning LIDAR Systems

FIG. 17 is a cross-sectional view of the construction of an exemplarylight transmission module 1700, according to some embodiments of thepresent disclosure. Light transmission module 1700 can include anemitter array 1702 formed on a substrate 1704. For example, in someembodiments emitter array 1702 can be a VCSEL array formed directly on asemiconductor chip. Emitter array 1702 can be mounted on a structure1706, e.g. a ceramic plate, along with driver circuitry (not shown) asdiscussed herein with respect to FIGS. 6 and 7A-7B, and structure 1706can be mounted on an interconnection structure 1708, e.g., a printedcircuit board (PCB). In some embodiments, structure 1706 can be drivercircuitry, such as a driver ASIC, that can operate emitter array 1702.When configured as driver circuitry, structure 1706 can be flip-chipbonded to an underside of substrate 1704. Various other electricalcomponents (not shown) can also be mounted on interconnection structure1708 to operate emitter array 1702. Thus, interconnection structure 1708can be electrically coupled with substrate 1704 via any suitable method,such as wire bonds (not shown).

In some embodiments, light transmission module 1700 can include a heatsink 1716 that is coupled to interconnection structure 1708 on a sideopposite from the side on which emitter array 1702 is coupled. That way,heat sink 1710 can draw heat away from emitter array 1702 duringoperation to prevent overheating. To provide this capability, variouscomponents can include heat routing structures to enable heat transferfrom emitter array 1702 to heat sink 1710. For instance, lighttransmission module 1700 can include a thermoelectric cooler (TEC) 1712between heat sink 1710 and interconnection structure 1708 to route heatgenerated by emitter array 1702 to heat sink 1710 or to regulate thetemperature of emitter array 1702. TEC 1712 can include two platessandwiching a plurality of thermally conductive vias, as shown in FIG.17. Heat sink 1710 can be any suitable heat sink that can dissipate heatinto the ambient environment, such as a metal structure with fins. Insome embodiments, interconnection structure 1708 can include an array ofthermal vias 1714 that extend between top and bottom surfaces ofinterconnection structure 1708 to thermally couple support structure1706, substrate 1704, and emitter array 1702 to heat sink 1710. Thermalvias 1714 can be formed of any suitable highly thermally conductivematerial, such as tungsten, copper, aluminum, or any other metalmaterial.

V. Exemplary Implementations for Scanning LIDAR Systems

Electronic scanning LIDAR systems, according to some embodiments of thepresent disclosure, can be configured as a solid state system that has astationary architecture. Such LIDAR systems do not rotate, and thus donot need a separate motor to rotate the sensor and transmitter modules.Example solid state LIDAR systems are shown in FIGS. 18 and 19.

FIGS. 18 and 19 are simple illustrations of exemplary implementations ofsolid state electronic scanning LIDAR systems. Specifically, FIG. 18illustrates an implementation 1800 where solid state electronic scanningLIDAR systems 1802 a-d are implemented at the outer regions of a roadvehicle 1805, such as an automobile, according to some embodiments ofthe present disclosure; and FIG. 19 illustrates an implementation 1900where solid state electronic scanning LIDAR systems 1902 a-b areimplemented on top of a road vehicle 1905, according to some embodimentsof the present disclosure. In each implementation, the number of LIDARsystems, the placement of the LIDAR systems, and the fields of view ofeach LIDAR system can be chosen to obtain a majority of, if not theentirety of, a 360 degree field of view of the environment surroundingthe vehicle. Automotive implementations for the LIDAR systems are chosenherein merely for the sake of illustration and the sensors describedherein may be employed in other types of vehicles, e.g., boats,aircraft, trains, etc., as well as in a variety of other applicationswhere 3D depth images are useful, such as medical imaging, mobilephones, augmented reality, geodesy, geomatics, archaeology, geography,geology, geomorphology, seismology, forestry, atmospheric physics, laserguidance, airborne laser swath mapping (ALSM), and laser altimetry.

With reference to FIG. 1800, solid state electronic scanning LIDARsystems 1802 a-d can be mounted at the outer regions of a vehicle, nearthe front and back fenders. LIDAR systems 1802 a-d can each bepositioned at a respective corner of vehicle 1805 so that they arepositioned near the outermost corners of vehicle 1805. That way, LIDARsystems 1802 a-d can better measure the distance of vehicle 1805 fromobjects in the field at areas 1806 a-d. Each solid state LIDAR systemcan face a different direction (possibly with partially and/ornon-overlapping fields of views between units) so as to capture acomposite field of view that is larger than each unit is capable ofcapturing on its own. Objects within the scene can reflect portions oflight pulses 1810 that are emitted from LIDAR Tx module 1808. One ormore reflected portions 1812 of light pulses 1810 then travel back toLIDAR system 1802 a and can be received by Rx module 1809. Rx module1809 can be disposed in the same housing as Tx module 1808. As discussedherein, electronic scanning LIDAR systems 1802 a-d can electronicallyscan a scene to capture images of the scene. Thus, LIDAR system 1802 acan scan between points 1820 and 1822 to capture objects in the field atarea 1806 a, and likewise for systems 1802 b-d and areas 1806 b-d.

Although FIG. 18 illustrates four solid state electronic scanning LIDARsystems mounted at the four corners of a vehicle, embodiments are notlimited to such configurations. Other embodiments can have fewer or moresolid state electronic scanning LIDAR systems mounted on other regionsof a vehicle. For instance, electronic scanning LIDAR systems can bemounted on a roof of a vehicle, as shown in FIG. 19. In suchembodiments, electronic scanning LIDAR systems 1902 a-b can have ahigher vantage point to better observe areas 1907 a-b around vehicle1905. In some embodiments, the scanning can be implemented by othermeans, such as chip-based beam steering techniques, e.g., by usingmicrochips that employ one or more MEMS based reflectors, such as adigital micromirror (DMD) device, a digital light processing (DLP)device, and the like, as will be discussed further herein with respectto FIGS. 9A-9B.

As mentioned herein, the number of LIDAR systems, the placement of theLIDAR systems, and the fields of view of each LIDAR system can be chosento obtain a majority of, if not the entirety of, a 360 degree field ofview of the environment surrounding the vehicle. Accordingly, each LIDARsystem 1802 a-d can be designed to have a field of view of approximately90 degrees so that when all four systems 1820 a-d are implemented, asubstantial majority of a 360 degree field of view around vehicle 1805can be observed. In embodiments where each LIDAR system 1802 a-d hasless than a 90 degree field of view, such as a 45 degree field of view,one or more additional LIDAR systems can be implemented so as to extendthe field of view to achieve a combined field of view greater than thatof a single LIDAR system, as will be discussed further herein withrespect to FIG. 20.

FIG. 20 is a simplified top-down illustration of an exemplary solidstate electronic scanning LIDAR system 2000 that includes more than oneset of emission and detection systems to achieve an expanded field ofview, according to some embodiments of the present disclosure. As shownin FIG. 20, solid state electronic scanning LIDAR system 2000 caninclude sets of emission and detection systems 2002 a-i mounted on acentral support structure 2004, where each set of emission and detectionsystems includes a respective light emission system, e.g., lightemission system 503 in FIG. 5, and light detection system, e.g. lightdetection system 501 in FIG. 5. Each set can be arranged radiallyoutward from the center of support structure 2004 and be positionedside-by-side so that their fields of view can abut one another to form acombined field of view 2006 that is a multitude times larger than afield of view for any single set of emission and detection systemsalone. The multiple emission detection systems may all be synchronizedand controlled by a common LIDAR controller such that the end userinteracts with what appears to be a single system. In addition, theindividual emission detection systems may all be aligned to a fixedpixel grid so that the date simulate a wider field of view, higherresolution system operating on a fixed field of view grid.

VI. Mitigating Receiver Channel Cross-Talk

As can be appreciated by disclosures herein, adjacent channels in thereceiving element can be positioned very close to one another (e.g.,within 100 microns of one another). Some embodiments of the disclosureinclude one or more structures that minimize cross-talk that mayotherwise occur between adjacent channels due to the tight pitch of thereceiving element. Ideally, no stray light should be received by anychannel, as shown in FIG. 21A.

FIG. 21A is a simplified cross-sectional view diagram of part of a lightdetection system 2100 where there is no cross-talk between channels.During operation, perpendicular light rays 2102 and chief ray 2104 entera bulk imaging optic 2106 and produce light cone 2108. Light rays 2102and 2104 enter an aperture of aperture layer 2110 and enter collimatinglens 2111. Collimating lens 2111 accepts a limited range of incidentlight angles. For example, collimating lens 2111 can accept light raysat incident angles between +25 to −25 degrees relative to theperpendicular. FIG. 21A shows light cone 2108 with incident anglesbetween +25 to −25 degrees. The chief ray 2104 is the light ray thatpasses through the center of the aperture. In this example, the chiefray 2104 has an incident angle of 0 degrees on the collimating lens2111.

FIG. 21B is a simplified cross-sectional view diagram of part of a lightdetection system 2101 where there is cross-talk between channels. Inthis case, during operation, oblique light rays 2112 and chief ray 2114enter bulk receiver optic 2116 and later enter collimating lens 2121. Inthis example, collimating lens 2121 belongs to a micro-optic channelthat corresponds to a photosensor further from the center of the image.In this example, chief ray 2114 has an incident angle of −12 degrees andthe cone of focused light has incident angles between +12 degrees to −35degrees. Collimating lens 2121 rejects some of the light rays because itonly accepts light with incident angles between +25 to −25 degrees.Additionally, the rays that are outside of the collimating lensacceptance cone can travel to other optical surfaces and become straylight. Thus, a non-telecentric bulk imaging optic will deliversignificantly fewer signal photons to the photodetector, whilepotentially polluting other channels with errant light rays 2122. Atelecentric bulk imaging optic, on the other hand, will produce lightcones with incident angles approximately between +25 to −25 degrees andchief rays with incident angles on the collimating lens of approximately0 degrees, regardless of the angle of the oblique rays 2112 and chiefray 2114. A telecentric bulk imaging optic has similar benefits for thetransmitter when the lasers are telecentric (their chief rays are allparallel) as is the case for VCSELS or a side emitter diode laser bar.

In some embodiments, the light detection system of a light sensingmodule uses an input image-space telecentric bulk imaging optic. In someother embodiments, for example where cost or increased field of view ismore important than performance, the light detection system may use amore standard input bulk imaging optic such as a bi-convex lens. For anygiven input field into an image-space telecentric lens, the resultingchief rays are parallel to the optical axis, and the image-side raycones all span approximately the same set of angles. This allowsmicro-optic channels far from the optical axis in the light detectionsystem to achieve similar performance to the on-axis micro-opticchannel. The light detection system does not need perfect image spacetelecentricity for this to work, but the closer to perfecttelecentricity the better. For a micro-optic receiver optical layer lensthat can only accept +/−25 degree light, the preference is that theinput bulk imaging optic produce image-side rays that are no greaterthan 25 degrees in angle for every point on the focal plane.

In certain embodiments, specific light detection systems having widefield of view and narrowband imaging can have an input image-spacetelecentric bulk imaging optic with a numerical aperture (NA) equal to0.34 and focal length of 20 mm. Similarly, some other embodiments couldhave a 1 nm wide bandpass filter, thereby enabling it to detect light ofa very specific wavelength. The light detection system is capable ofsupporting FOVs greater than 30 degrees.

According to some embodiments of the present disclosure, the design ofeach channel of the micro-optic receiver channel array can bespecifically configured to have features that minimize the intrusion ofstray light onto a respective photodetector, thereby reducing oreliminating any detrimental effects caused by the occurrence of straylight. FIG. 22 is a simplified cross-sectional diagram of an exemplarymicro-optic receiver channel structure 2200, also called a micro-opticreceiver channel in discussions herein. Receiver channel 2200 can berepresentative of micro-optic receiver channels 512 in FIG. 5, andserves to accept an input cone of light containing a wide range ofwavelengths, filters out all but a narrow band of those wavelengthscentered at the operating wavelength, and allows photosensor 2202 todetect only or substantially only photons within the aforementionednarrow band of wavelengths. According to some embodiments of the presentdisclosure, micro-optic receiver channel structures, such as receiverchannel 2200, can include the following layers:

-   -   An input aperture layer 2204 including an optically transparent        aperture 2206 and optically non-transparent stop region 2208        configured to define a narrow field of view when placed at the        focal plane of an imaging optic, such as bulk receiver optic 502        shown in FIG. 5 (not shown in FIG. 22). Aperture layer 2204 is        configured to receive the input marginal ray lines 2210. The        term “optically transparent” herein refers to as allowing most        or all light to pass through. Light herein refers to the        spectrum of electromagnetic radiation in the near-ultraviolet,        visible, and near-infrared range (e.g. 300 nm to 5000 nm).        Optically non-transparent herein refers to as allowing little to        no light to pass through, but rather absorbing or reflecting the        light. Aperture layer 2204 can include an array of optically        transparent apertures of uniform area (e.g., each aperture can        be a pinpoint hole having the same diameter) separated from each        other by optically non-transparent stop regions. The apertures        and stop regions can be built upon a single monolithic piece        such as an optically transparent substrate. Aperture layer 2204        can optionally include a one-dimensional or two-dimensional        array of apertures 2206.    -   An optical lens layer 2212 including a collimating lens 2214        characterized by a focal length, offset from the plane of        aperture 2206 and stop region 2208 by the focal length, aligned        axially with aperture 2206, and configured to collimate photons        passed by the aperture such that they are traveling        approximately parallel to the axis of collimating lens 2214        which is aligned with the optical axis of receiver channel 2200.        Optical lens layer 2212 may optionally include apertures,        optically non-transparent regions and tube structures to reduce        cross talk.    -   An optical filter layer 2216 including an optical filter 2218,        typically a Bragg reflector type filter, adjacent to collimating        lens 2214 and opposite of aperture 2206. Optical filter layer        2216 can be configured to pass normally incident photons at a        specific operating wavelength and passband. Optical filter layer        2216 may contain any number of optical filters 2218. Optical        filter layer 2216 may optionally include apertures, optically        non-transparent regions and tube structures to reduce cross        talk.    -   A photosensor layer 2220 including a photosensor 2202 adjacent        to optical filter layer 2216 and configured to detect photons        incident on photosensor 2202. Photosensor 2202 herein refers to        a single photodetector capable of detecting photons, e.g., an        avalanche photodiode, a SPAD (Single Photon Avalanche Detector),        RCP (Resonant Cavity Photo-diodes), and the like, or several        photodetectors, such as an array of SPADs, cooperating together        to act as a single photosensor, often with higher dynamic range,        lower dark count rate, or other beneficial properties as        compared to a single large photon detection area. Each        photodetector can be an active area that is capable of sensing        photons, i.e., light. In some embodiments, the photosensor layer        includes an array of photodetectors, each of which has a        substantially uniform sensing area that is larger than the area        of its corresponding aperture in aperture layer 2204. In        embodiments where each photosensor is an array of SPADs or other        photodetectors, the SPADs or other photodetectors of a given        photosensor are distributed across the sensing area. Photosensor        layer 2220 refers to a layer made of photodetector(s) and        contains optional structures to improve detection efficiency and        reduce cross talk with neighboring receiver structures.        Photosensor layer 2220 may optionally include diffusers,        converging lenses, apertures, optically non-transparent tube        spacer structures, optically non-transparent conical spacer        structures, etc.

Stray light may be caused by roughness of optical surfaces,imperfections in transparent media, back reflections, and the like, andmay be generated at many features within the receiver channel 2200 orexternal to receiver channel 2200. The stray light may be directed:through the filter region 2218 along a path non-parallel to the opticalaxis of collimating lens 2214; reflecting between aperture 2206 andcollimating lens 2214; and generally taking any other path or trajectorypossibly containing many reflections and refractions. If multiplereceiver channels are arrayed adjacent to one another, this stray lightin one receiver channel may be absorbed by a photosensor in anotherchannel, thereby contaminating the timing, phase, or other informationinherent to photons. Accordingly, receiver channel 2200 may featureseveral structures to reduce crosstalk between receiver channels.

According to some embodiments, each layer of a micro-optic channel layerstructure can be designed a specific way to mitigate the detrimentaleffects of stray light. Various different designs for each layer arediscussed in U.S. patent application Ser. No. 15/979,295, entitled“Micro-optics for Imaging Module with Multiple Converging Lenses perChannel”, filed on May 14, 2018, and incorporated by reference hereinfor all purposes.

Each such layer can be configured in various ways to mitigatecross-talk. i.e., exposing stray light to adjacent receiver channels, asdiscussed herein with respect to FIG. 22; however, embodiments of thepresent disclosure are not limited to that particular configuration, andthat other embodiments can be configured in different ways using thedifferent embodiments of the respective layers disclosed in the U.S.patent application Ser. No. 15/979,295 mentioned above.

As can be appreciated in FIG. 22, a receiver channel can include aplurality of layers that perform specific functions. With each layer,however, there is an associated manufacturing cost. Thus, greaternumbers of layer can sometimes result in a higher manufacturing cost. Insome instances, it may be desirable to remove one or more layers orsimplify the construction of the receiver channel to save cost withoutsignificantly impacting the sensing ability of the receiver channel. Anexample of such a simplified receiver channel is discussed herein withrespect to FIG. 23.

FIG. 23 is a simplified cross-sectional view diagram of an exemplarysimplified receiver channel 2300, according to some embodiments of thepresent disclosure that is well-suited for embodiments where thephotosensors (e.g., arrays of SPADs) are packed very tightly togetherand, due to tight spacing, the aperture of the receiver channel is madesmaller. For example, in a rotating LIDAR application where thephotosensor array includes an array of SPADs, the array may be designedto have a pixel pitch of 200 microns or even 400 microns. To achieve acompetitive resolution in some solid-state LIDAR designs, the pixels arepacked together at an even tighter pitch, for example, 100 microns orless. With larger 200-400 micron channels, the aperture of each sensorchannel (e.g., aperture 2304) in some instances may be about 25-30microns in diameter. As the sensor channel is condensed to the smallerpitch (e.g., 100 microns), the diameter of the aperture can also becondensed. The reduced pitch and smaller aperture combine such that thebenefit of including a lens layer to collimate the rays passing throughthe aperture may not be worth the additional processing steps offabricating the lens.

As shown in FIG. 23, receiver channel 2300 can include an aperture layer2302 including an aperture 2304 formed in a non-transparent layer 2306.Aperture 2304 can be formed of void space defined by openings withinlayer 2306 in some embodiments, while apertures 2304 can be formed byoptically transparent materials in some other embodiments.

Receiver channel 2300 can further include an optical filter layer 2314positioned directly above aperture layer 2302 as illustrated in FIG. 23,or positioned between aperture 2302 and photosensors 2326. Opticalfilter layer 2314 can include an optical filter 2316 positioned directlyon an optically transparent substrate 2318 that structurally supportsoptical filter 2316. As can be appreciated by comparison with FIGS. 14and 15, receiver channel 2300 does not include an optical lens layer forcollimating light that enters aperture 2304. By removing the opticallens layer, receiver channel 2300 can have a simpler design with lesslayers. The sacrifice in optical performance for not including theoptical lens layer may not outweigh the cost savings and simplicity inmanufacturing the receiver channel. Furthermore, one or more otherlayers of receiver channel 2300 can be modified to compensate for theabsence of the optical lens layer. For example, optical filter 2316 canbe modified to be a wider bandpass filter than optical filters 2218 inFIG. 22. By not having an optical lens layer, the incoming light aremore angled and thus will include a broader spectrum of wavelengths.Thus, by having being a wider bandpass filter that has a wider pass bandto allow a broader spectrum of light through optical filter 2316. Insome embodiments, optical filter 2316 is an order of magnitude greaterin pass band width than optical filters 1416 and 1516, such as between9× and 11× magnitude, particularly 10× magnitude, greater in someparticular embodiments. Thus, as an example, optical filter 2316 canhave a 10 nm wide pass band instead of a 1 nm pass band for opticalfilters 1416 and 1516.

Immediately below aperture layer 2302 can be a photosensor layer 2320.In some embodiments, photosensor layer 2320 of receiver channel 2300 caninclude an optically non-transparent spacer structure 2322, a converginglens set 2324, and a photosensor 2326. Converging lens set 2324 can bepositioned directly on at top surface of photosensor 2326, and includeone converging lens per discrete photodetector 2328 within photosensor2326, where each lens of the converging lens set 2324 is configured tofocus incident photons passed by optical filter layer 2314 and aperture2304 onto a corresponding discrete photodetector 2328, rather thaninactive areas 2330. Furthermore, optically non-transparent spacerstructure 2322 can be formed of an optically non-transparent material(e.g., black chrome). Optically non-transparent spacer structure 2322forms a tube that prevents any light from traveling outside of receiverchannel 2300 in the region between photosensor 2326 and aperture layer2302.

According to some embodiments of the present disclosure, by positioningaperture 2304 in front of its respective photosensor, aperture 2304constrains the field of view that is detected by photosensor 2326,thereby improving the spatial acuity of photosensor 2326 becauseaperture 2304 forces photosensor 2326 to observe only a single point inthe field. Aperture 2304 also provides filtering functionality to onlyallow light that is propagating at certain angles to enter the receiverchannel and be exposed onto photosensor 2326, or all the SPADS ifphotosensors 2326 is arranged as an array of SPADS. In some embodiments,the size of aperture 2304 is smaller than the size of photosensor 2326.

By implementing a receiver channel according to any of embodimentsdiscussed herein with respect to FIG. 23, errant light can be preventedfrom exposing on adjacent receiver channels, thereby improving theaccuracy of each photosensor's ability to capture photons for imaging.

VII. Electronic Scanning LIDAR System Specifications

As can be appreciated by embodiments of the present disclosure, thefield of view and resolution of a particular LIDAR system can depend onseveral interrelated factors, such as, but not limited to, size of thesensor array, pitch of the photosensors in the sensor array, pitch ofthe emitter array, size of the emitter array, and the pitch of the SPADsin a single photosensor. Larger sensor arrays can result in larger fieldof views where the size of the sensor pitch is constant. Additionally,smaller photosensor pitches can result in higher resolution images ininstances where the size of the sensor array is constant, but can resultin smaller fields of view.

To meet the requirements of some commercial LIDAR specifications,electrical scanning LIDAR systems can be designed various ways. Forexample, some commercial LIDAR specification require a minimum field ofview of approximately 45 degrees in the horizontal direction and 22.5degrees in the vertical direction, and a minimum resolution ofapproximately 256 pixels by 128 pixels. Thus, some scanning LIDARsystems can be designed to meet these requirements by being configuredwith a sensor array having a 256 by 128 sensor array. To keep the sizeof the array compact, the photosensor pitch can range between 50 to 70um, particularly 60 um in certain embodiments in both the vertical andhorizontal dimensions; and in embodiments where each photosensor isformed of an array of SPADS, the SPAD pitch can range between 5 to 15um, particularly 10 um in certain embodiments. In such embodiments, eachphotosensor can have 16 SPADS. The resulting size of the sensor arraycan be approximately 15 mm×7.6 mm.

To ensure that the sensor array receives enough light, the emitter arraycan be designed to complement the specifications of the sensor array.For instance, the emitter array can be formed of two emitter arrays(which results in a LIDAR system with two light emission systems), wherethe emitter arrays are each sparse emitter arrays that can combine toachieve a resolution greater than each of them alone, as discussedherein with respect to FIG. 8A. As a combination, the emitter arrays cangenerate an illumination pattern that matches the photosensorarrangement of the sensor array. Accordingly, each emitter can have sizeof approximately 7.6 mm×3.8 mm.

VIII. Positioning of Readout Lines for Sensor Arrays

As can be seen in FIGS. 11-13, the readout lines (indicated by thearrows in the respective sensor arrays 1102, 1202, and 1302) are shownoverlapping with the photosensors. In other embodiments, however, thesereadout lines can be rearranged to maximize the real estate forphotosensors. As an example, FIG. 24 is a simplified drawing of azoomed-in portion 2400 of a sensor array 2402, according to someembodiments of the present disclosure. A plurality of column enablelines 2404 and readout lines 2406 can exist to enable the operation ofphotosensors 2408. Instead of routing column enable lines 2404 andreadout lines 2406 through sensor array 2402 and in between photosensors2408, column enable lines 2404 and readout lines 2406 can be routedaround, i.e., near or outside of an outer perimeter of, sensor array2402. Additionally, when photosensors 2408 are SPADs, each SPAD requiresanalog front end components 2410, which can be solid state devices thatare configured for biasing, quenching, and recharging of photosensors2408 during operation, readout lines 2406 can also be routed outsidefront end components 2410. By routing column enable lines 2404 andreadout lines 2406 around sensor array 2402, photosensors 2408 can bepositioned so as to maximize the fill factor in their local area. Whenused in combination with a micro-lens array, this allows for highoptical fill factors at the photosensor level.

To provide even more space for photosensors 2408, one or more componentscan be mounted on a backside of the silicon substrate upon which thesensor array is disposed or on a different substrate altogether. As anexample, FIG. 25 is a simplified drawing of a zoomed-in portion 2500 ofa sensor array 2502 with one or more components mounted on a backside ofthe substrate, according to some embodiments of the present disclosure.A plurality of column enable lines 2504 and readout lines 2506 can existto enable the operation of photosensors 2508 and be positioned aroundsensor array 2502. Instead of having front end components positioned onthe front side of the substrate along with sensor array 2502, the frontend components can be mounted on the back side, thus freeing up morespace for photosensors 2508. As such, front end components 2410 seen inFIG. 24 are not present in FIG. 25 and the area in which sensor array2502 is positioned is increased. Accordingly, the resolution of thesensor array can be increased and the size of the chip can be decreased,thereby saving cost.

Although the present disclosure has been described with respect tospecific embodiments, it will be appreciated that the present disclosureis intended to cover all modifications and equivalents within the scopeof the following claims.

What is claimed is:
 1. An optical system for performing distancemeasurements, the optical system comprising: an illumination sourcecomprising a column of light emitters aligned to project discrete beamsof light into a field external to the optical system; a MEMS deviceconfigured to tilt along a scanning axis oriented perpendicular to thecolumn of light emitters and reflect radiation from the column into thefield to produce a two-dimensional illumination pattern in which thediscrete beams from the column of light emitters are repeated multipletimes forming multiple non-overlapping columns within the pattern; alight detection system configured to detect photons emitted from theillumination source and reflected from surfaces within the field, thelight detection system comprising a photosensor layer including atwo-dimensional array of photosensors having a sensing pattern in thefield that substantially matches, in size and geometry across a range ofdistances from the system, the two-dimensional illumination patterncreated by the MEMS device; circuitry coupled to the MEMS device and thecolumn of light emitters and configured to execute a plurality of imagecapture periods where, for each image capture period, the column oflight emitters is sequentially fired while the MEMS device is tiltedalong its axis until the illumination pattern is generated; and sensorarray scanning circuitry coupled to the array of photosensors andconfigured to synchronize the readout of individual photosensors withinthe array concurrently with the firing of corresponding emitters withinthe column of light emitters.
 2. The optical system of claim 1 whereinthe two-dimensional array of photosensors comprises m number ofphotosensors per row and n number of photosensors per column that formsan m×n array of photosensors.
 3. The optical system of claim 2 whereinthe illumination source is a one-dimensional array of light emitterscomprising n number of light emitters.
 4. The optical system of claim 3wherein the circuitry is configured to operate the illumination lightsource to emit the n number of light emitters simultaneously during eachimage capture period.
 5. The optical system of claim 4 wherein thecircuitry is further configured to operate the illumination source for mnumber of image capture periods while the MEMS mirror is continuouslytilting along the scanning axis to create the two-dimensionalillumination pattern, wherein the two-dimensional illumination patterncomprises m number of discrete beams of light per row into the fieldexternal to the optical system and n number of discrete beams of lightper column into the field external to the optical system that forms anm×n array of discrete beams of light into of the field external to theoptical system.
 6. The optical system of claim 1 wherein the MEMS deviceis a MEMS tilt mirror that tilts in one dimension along the scanningaxis.
 7. The optical system of claim 1 wherein the light detectionsystem further includes an aperture layer including a plurality ofapertures, wherein the aperture layer and the photosensor layer arearranged to form a plurality of sense channels.
 8. The optical system ofclaim 7 wherein each sense channel in the plurality of sense channelscorresponds to an emitter in the array of emitters and includes anaperture from the aperture layer and a photosensor from the photosensorlayer.
 9. An optical system for performing distance measurements, theoptical system comprising: a light emission system comprising a bulktransmitter optic, an illumination source comprising a column of lightemitters aligned to project discrete beams of light through the bulktransmitter optic into a field external to the optical system; a MEMSdevice disposed between the bulk transmitter optic and the illuminationsource, the MEMS device configured to tilt along a scanning axisoriented perpendicular to the column of light emitters and reflectradiation from the column into a field external to the optical system toproduce a two-dimensional illumination pattern in which the discretebeams from the column of light emitters are repeated multiple timesforming multiple non-overlapping columns within the pattern; a lightdetection system configured to detect photons emitted from theillumination source and reflected from surfaces within the field, thelight detection system comprising a bulk receiver optic, an aperturelayer including a plurality of apertures, and a photosensor layerincluding a two-dimensional array of photosensors, wherein the aperturelayer and the photosensor layers are arranged to form a plurality ofsense channels having a sensing pattern in the field that substantiallymatches, in size and geometry across a range of distances from thesystem, the two-dimensional illumination pattern created by the MEMSdevice, and wherein each sense channel in the plurality of sensechannels corresponds to an emitter in the array of emitters and includesan aperture from the aperture layer and a photosensor from thephotosensor layer; circuitry coupled to MEMS device and the column oflight emitters and configured to execute a plurality of image captureperiods where, for each image capture period the column of lightemitters is sequentially fired while the MEMS device is tilted along itsaxis to until the illumination pattern is generated; and sensor arrayscanning circuitry coupled to the array of photosensors and configuredto synchronize the readout of individual photosensors within the arrayconcurrently with the firing of corresponding emitters within the arrayof light emitters.
 10. The optical system of claim 9 wherein thetwo-dimensional array of photosensors comprises m number of photosensorsper row and n number of photosensors per column that forms an m×n arrayof photosensors.
 11. The optical system of claim 10 wherein theillumination source is a one-dimensional array of light emitterscomprising n number of light emitters.
 12. The optical system of claim11 wherein the circuitry is configured to operate the illumination lightsource to emit the n number of light emitters simultaneously during eachimage capture period.
 13. The optical system of claim 12 wherein thecircuitry is further configured to operate the illumination source for mnumber of image capture periods while the MEMS mirror is continuouslytilting along the scanning axis to create the two-dimensionalillumination pattern, wherein the two-dimensional illumination patterncomprises m number of discrete beams of light per row into the fieldexternal to the optical system and n number of discrete beams of lightper column into the field external to the optical system that forms anm×n array of discrete beams of light into of the field external to theoptical system.
 14. An optical system for performing distancemeasurements, the optical system comprising: a light emission systemcomprising a bulk transmitter optic, an illumination source comprising asingle light emitter aligned to a project discrete beam of light throughthe bulk transmitter optic into a field external to the optical system;an optical element disposed between the bulk transmitter optic and theillumination source and configured to generate a spot pattern from thesingle light emitter; a MEMS device disposed between the optical elementand the illumination source, the MEMS device configured to tilt along ascanning axis and reflect radiation from the single light emitter into afield external to the optical system to produce a two-dimensionalillumination pattern in which the spot pattern of light is repeatedmultiple times forming multiple non-overlapping columns within thepattern; a light detection system configured to detect photons emittedfrom the illumination source and reflected from surfaces within thefield, the light detection system comprising a bulk receiver optic, anaperture layer including a plurality of apertures, and a photosensorlayer including a two-dimensional array of photosensors, wherein theaperture layer and the photosensor layers are arranged to form aplurality of sense channels having a sensing pattern in the field thatsubstantially matches, in size and geometry across a range of distancesfrom the system, the two-dimensional illumination pattern created by theMEMS device, and wherein each sense channel in the plurality of sensechannels corresponds to a spot within the two-dimensional illuminationpattern and includes an aperture from the aperture layer and aphotosensor from the photosensor layer; circuitry coupled to MEMS deviceand the single light emitter and configured to execute a plurality ofimage capture periods where, for each image capture period the singlelight emitter is sequentially fired while the MEMS device is tiltedalong its axis until the illumination pattern is generated; and sensorarray scanning circuitry coupled to the array of photosensors andconfigured to synchronize the readout of individual photosensors withinthe array concurrently with the firing of the single light emitter. 15.The optical system of claim 14 wherein the optical element is adiffractive optical element configured to diffract the discrete beam oflight emitted from the single light emitter into a one-dimensional arrayof discrete beams of light, wherein the one-dimensional array ofdiscrete beams of light comprises n number of discrete beams of light.16. The optical system of claim 15 wherein the scanning axis of the MEMSdevice is oriented perpendicular to the one-dimensional array ofdiscrete beams of light.
 17. The optical system of claim 16 wherein thecircuitry is further configured to operate the illumination source for mnumber of image capture periods while the MEMS mirror is continuouslytilting along the scanning axis to create the two-dimensionalillumination pattern.
 18. The optical system of claim 17 wherein thetwo-dimensional illumination pattern comprises m number of discretebeams of light per row into the field external to the optical system andn number of discrete beams of light per column into the field externalto the optical system that forms an m×n array of discrete beams of lightinto of the field external to the optical system.
 19. The optical systemof claim 19 wherein the two-dimensional array of photosensors comprisesm number of photosensors per row and n number of photosensors per columnthat forms an m×n array of photosensors.
 20. The optical system of claim14 wherein the MEMS device is a MEMS tilt mirror that tilts in onedimension along the scanning axis.